The following radio instructions are for the non-computer screen type:
To reset the radio code:
1- Turn ignition on
2- Turn radio on; display will read "CODE"
3- Enter your 5-digit radio code (the numbers will not be echoed on the display screen); radio will switch to FM
4- If you enter in a wrong number, go ahead and enter more digits so that a total of 5 have been entered; radio will not operate; re-enter the correct 5-digit code; radio will switch to FM. If you fail three times, you have to leave the radio ON for 1 hour before you can try again.
Sorry you've had so much trouble. If you're a pretty handy DIYer there's lots of help available. Here's one really good website:
http://www.nmia.com/~dgnrg/page_2.htm
Also consider joining
www.roadfly.com where there is a LOT of help. Good luck.