[Android Head-Units] donaldta:
Probably the easiest and safest way is with Titanium Backup and opt to backup everything, data+app. Alternatively, you can use ES File Explorer to backup the APK with its App Manager but then you'd have to use another manual method of the other files, like the maps. You should be able to get a listing of all the relevant directories by querying the package through dumpsys as root which can be done through "adb shell" or Android terminal.

Here is an example from my Asteroid Smart to find the correct directories to back up (highlighted in red, actual values might differ on your unit)

$ [COLOR="RoyalBlue"][B]su[/B][/COLOR]
# [COLOR="RoyalBlue"][B]dumpsys package com.sygic.aura[/B][/COLOR]
Activity Resolver Table:
Full MIME Types:
vnd.android.cursor.item/postal-address_v2:
409ae138 com.sygic.aura/.SygicNaviActivity filter 409696d0

Base MIME Types:
vnd.android.cursor.item:
409ae138 com.sygic.aura/.SygicNaviActivity filter 409696d0

Schemes:
fb105659562809354:
409ae138 com.sygic.aura/.SygicNaviActivity filter 40969360
https:
409ae138 com.sygic.aura/.SygicNaviActivity filter 409d56a0
geo:
409ae138 com.sygic.aura/.SygicNaviActivity filter 409698c0
google.navigation:
409ae138 com.sygic.aura/.SygicNaviActivity filter 4084e350
db-jlti4f13g1dbwhb:
409ae138 com.sygic.aura/.SygicNaviActivity filter 40969a68
http:
409ae138 com.sygic.aura/.SygicNaviActivity filter 409ae558
409ae138 com.sygic.aura/.SygicNaviActivity filter 409d56a0
ssogoogle:
409ae138 com.sygic.aura/.SygicNaviActivity filter 40969520
com.sygic.aura:
409ae138 com.sygic.aura/.SygicNaviActivity filter 409ae918

Non-Data Actions:
android.intent.action.MAIN:
409ae138 com.sygic.aura/.SygicNaviActivity filter 409ae2a0

MIME Typed Actions:
android.intent.action.VIEW:
409ae138 com.sygic.aura/.SygicNaviActivity filter 409696d0

Receiver Resolver Table:
Non-Data Actions:
com.google.android.c2dm.intent.RECEIVE:
40865648 com.sygic.aura/.c2dm.C2DMReceiver filter 408657e8
com.google.android.c2dm.intent.REGISTRATION:
40865648 com.sygic.aura/.c2dm.C2DMReceiver filter 408657e8
com.android.vending.INSTALL_REFERRER:
4098c3b8 com.sygic.aura/com.google.android.apps.analytics.AnalyticsReceiver filter 4098c4f8

Service Resolver Table:
Non-Data Actions:
com.sygic.intent.action.bindRemoteService:
40865398 com.sygic.aura/.SygicService filter 40865488
com.sygic.aura.IRemoteService:
408650a8 com.sygic.aura/.RemoteService filter 40865180
com.sygic.aura.SYGIC_SERVICE:
408650a8 com.sygic.aura/.RemoteService filter 40865180

Permissions:
Permission [com.sygic.aura.permission.C2D_MESSAGE] (40a04070):
sourcePackage=com.sygic.aura
uid=10069 gids=[] type=0 prot=2
packageSetting=PackageSetting{409b4428 com.sygic.aura/10069}
perm=Permission{40947fd8 com.sygic.aura.permission.C2D_MESSAGE}

Packages:
Package [com.sygic.aura] (409b4428):
userId=10069 gids=[3003, 1015, 1006, 1007]
sharedUser=null
pkg=Package{409371a0 com.sygic.aura}
[COLOR="Red"][B]codePath=[/B][/COLOR]/data/app/com.sygic.aura-1.apk
[COLOR="Red"][B]resourcePath=[/B][/COLOR]/data/app/com.sygic.aura-1.apk
[COLOR="Red"][B]nativeLibraryPath=[/B][/COLOR]/data/data/com.sygic.aura/lib
versionCode=67
versionName=13.4.1
[COLOR="Red"][B]dataDir=[/B][/COLOR]/data/data/com.sygic.aura
targetSdk=18
supportsScreens=[small, medium, large, xlarge, resizeable, anyDensity]
timeStamp=2014-01-13 17:06:22
firstInstallTime=2014-01-13 17:06:34
lastUpdateTime=2014-01-13 17:06:34
signatures=PackageSignatures{408cad18 [40801018]}
permissionsFixed=true haveGids=true
pkgFlags=0x0 installStatus=1 enabled=0
grantedPermissions:
com.android.launcher.permission.INSTALL_SHORTCUT
com.sygic.aura.permission.C2D_MESSAGE
android.permission.WRITE_EXTERNAL_STORAGE
android.permission.READ_LOGS
android.permission.ACCESS_WIFI_STATE
android.permission.ACCESS_COARSE_LOCATION
android.permission.READ_CONTACTS
android.permission.CALL_PHONE
com.google.android.c2dm.permission.RECEIVE
android.permission.MODIFY_AUDIO_SETTINGS
android.permission.READ_PHONE_STATE
com.android.vending.BILLING
android.permission.CAMERA
android.permission.INTERNET
android.permission.CHANGE_WIFI_STATE
android.permission.ACCESS_LOCATION_EXTRA_COMMANDS
android.permission.ACCESS_FINE_LOCATION
com.android.vending.CHECK_LICENSE
android.permission.VIBRATE
android.permission.WAKE_LOCK
android.permission.ACCESS_NETWORK_STATE
#

Check my Post #1044 for the instructions. I believe you would select the one that says, "4.0.6, RDS, Rohm37534, TEF66xx". Though, I believe "4.0.6" number actually changes with the firmware version, so it may appear differently depending on the version you had installed. The rest of it are just options to the MCU as also explained in the post. I believe this is the process to update the MCU which is responsible for many of the low level functions that are not managed by Android directly. Though, I believe it is possible that it may not be necessary for a "minimal" upgrade, but most likely to be necessary for a "complete" upgrade.

He might be confusing the dual OS units which have two separate SD Card slots. In those units, one slot was meant for your media files, the other one was dedicated for maps. However, this is because the map SD card was linked to the Windows CE and the other to Android. On some units you might be able to see the outline of where the second slot could be.

In any case, for the AN 21-U units with "pure" Android 4.1 there is only one slot which is mounted on /mnt/usb/mmcblk1p1 and also has a /extsd symlink which points to it. The "other" SD Card is a partition of the internal system flash drive and is mounted on /mnt/sdcard which also has /sdcard symlink pointing to it.