sorry to hear you got jipped... you should try contacting the seller and get another unit or your money back from them... if its only a couple weeks, you may still have a chance.
Not to degrade you, but if you have to ask if its user servicable, it is not servicable by you. I only say this because if you know what you are doing, sometimes you can poke around inside the unit for a while and find something... but it takes quite a bit of electronics know-how. I cannot say im the greatest at fixing things like this (ive f'ed up a couple things before trying to fix them), but I have a good idea how things should look and work.
They are pretty complicated inside, and I'd hate to see you open it up and screw something else up, so I really do not advise you putts around with it.
What exactly do you mean "it wont accept CD's anymore" ? The cd player just wont let you insert a CD? You get error messages?? what exactly does the unit do?
If worst comes to worst... you could find a used alpine changer on ebay for like $50... then just leave the cd slot for decoration.