antenna adapters needed for RF-CD changer in 99 C-230?

I've been looking to upgrade my anemic system by adding a Pioneer CDX-1277 RF-FM 12 disk changer and a simple amplified bass tube but wonder about potential problems.

1. Where is my antenna, cable, and can I conveniently access it? A convenient call to Crutchfield's techies told me that if the 99 C-230 used the same cable and connectors as the 98 ML-320, there would be no problem. Anyone know if they're the same?

2. Is there a good source of power for the CD-changer and say, a 150 watt amplified tube in the trunk? Do I have to run a wire from the dash?

3. Can I grab audio feed from the rear speakers for the sub, or must I remove the radio and splice into the audio output?

4. Would it be cheaper and easier to avoid the sub, and merely upgrade the existing speakers with premium speakers?

If at all possible, I'd like to avoid the need to run cables from the front of the car.

Any advice would be great!

Thanks,
Glenn