['93 190e 2.6] General Radio Questions

Hello everyone. I was hoping I could ask all of you for some help with my radio. I'm definitely not a "do it yourselfer," and sure do wish that I was. I'm looking into the possibility of getting a different radio for my car, one with a CD player. Specifically, here are the questions that I have:

1. I have a front speaker on the driver's side that I think is dead. It works sometimes, but mostly, it doesn't. All of the other speakers seem to be OK. Can I just replace the one speaker, or do I have to replace all of them?

2. I have the standard Mercedes-Benz radio with the tape player. It's the factory one. Can I just get a different radio and have it installed in there to replace the old one?

3. I've read some posts and it talks about an amplifier. I dunno -- do I have to worry about this? Do I even have one of these??

I'm just looking for a decent CD player and a replacement for that front speaker -- nothing fancy, but which will do the job. About how much would you think I would have to pay to have a CD player put in? What recommendations would you have for an affordable, but yet decent, model?

Thanks very much for your help!