At first learning assembly may seem daunting when faced with pages full of what seem to be randomly chosen letters in no apparent arrangement. This allows for a very high degree of efficiency, but it can also easily crash the system. Probably the one really easy part of assembly programming is the fact that IF you do make an error, you'll know it.
Assembly programming requires a decent assembler and a computer.
By far the best assembler I've seen is Assembly Studio 86 by Jeremy Goetsch. In it you can create and edit source code, assemble and link it, and you get it prepackaged in a nice .86p format, ready to send to your calculator with the built in CalcExplorer uploader. You can find this marvelous program at the Assembly Studio site. Unless you want to spend three hours punching in seemingly meaningless hex codes on the calc's keypad, you'll want a way to get the program from the computer to the calculator. You can buy a GraphLink cable from Texas Instruments for an exorbitant sum or you can make your own parallel or serial port interface.