I'm glad you asked slietesa..
I actually fixed my problem. Well, the problem with the number five preset was caused by me not securely tightening everything back up after I took out the nav screen. I think the radio faceplate had troubles making contacts.
To fix the cd error message.. I took out the cd changer unit, I took off the top cover exposing the insides of the changer. I had six cd's in there. I think the order of which the cd's were in.. or like the order of which the mechanical parts were in, got mixed up.
Now this part, I thought I had broken it.. But it went back together and works perfectly now.. I took the 5 cd's that weren't on the spinner out through the back of their holders. I should have took some pictures... If you have the faceplate facing you and your looking down at the top of the unit without a cover, I lifted up the metal top of where the cd's were almost an inch, there is a few pins that go through the plastic cd holders, and one pin came out of place. I went slow, lifting up just enough to wiggle out the cd's through the back. When I had the five cd's out, i let the metal peice back down trying to work it back in through the holes in the plastic cd holder. It kind of fell back in place where it was supposed to be. I was pretty nervous the whole time. I had one cd in place where it spins and plays.. i didn't bother trying to take that one out. I put the cover back on, plugged it in to the car and it loaded right up and when i pressed Cd it played the cd in place... it works perfectly now. it loads and ejects a full six cd's too.
Another thing I'll note is that before I took it apart I noticed a couple things. If you unplug the unit and plug it back in, you can't hear any moving parts. But if you unplug the battery of the car or have the unit unplugged for like 30 minutes, and when you turn it back on, you can hear the changer moving around to read how many cd's are in place. I think that's the important part that will cause an error. If the position of the cd's are messed up or jammed, it won't know how many cd's are in and wont let you do anything with the cd changer. So that would make sense that people have problems occasionally, and it can sometimes be solved by unplugging battery.
One more thing, while this fixed my problem, I don't know if it will for you... but it's probably a good thing to try as long as your careful.
Oh and by the way.. it was against my business interests to give you that advice. Because I'm actually selling my bose cd changer on ebay right now. So if for some reason you can't fix it.. I have 5 days left on my auction and I started the bidding at $50 with $20 shipping.. Other auctions have a buy now of $80-120.