Help/Questions for 300E Stereo System Install

I have a few questions.

My Becker Grand Prix just started smoking after a few days of not working. That is quality. I really think the stereo system from these Beckers were really crappy. I can't wait to rip all that crap out. Just to see what replacement Beckers cost, I went to www.adsitco.com and they say about $550. Whoever would spend that much money on a crappy tape player deserves to be shot in the knees, unless you want it as a antique or something !

Anyway, maybe I can get some answers to these questions..
I am a big audio guy, but not a car audio guy

1.If I purchase a sony cd/mp3 player for my 300e, will it be compatible with my power antenna (which I replaced a few months earlier to this stupid problem?)

2.Will this replace screw up my alarm system?

3.People were talking about optical and coaxial connections for the speakers to the head unit. Is it difficult to rewire the car, or can we just use the original wires? I'm just going to install 2 new front and rear speakers, no subs or amps, can't I just use the original wires? is this bad?

I appreciate everyones help on the other forums. It will make this self installation (my first, and probably most difficult) much easier. I will definetly follow any recommendations for which speakers to use. By the way, how is Bose for the rear?

Thanks in advance!