Check with the owner's manual before venturing in to clean the keyboard. To clean the board without disassembling the board you can turn the keyboard upside-down and with the compressed air, blow all the dust and debris out from between the keys. Some people find that after using a mouse for a while that they may begin to lose their accuracy and this will cause some people to go out and immediately purchase a new mouse. This is usually unnecessary. The mouse is the easiest part of the computer to clean.
Most mice have a track ball.
To remove the track ball you will just need to turn the little piece that holds the ball in and the track ball will usually pop right out. Inside are wheels and rollers. On these you will see some matted down lint clinging to the wheels and rollers. To remove this you can use your fingernail to gently scrape this lint off. Check to make sure there are no hairs bound up in the rollers.