Is it true that to replace the rear fender that you have to take off the whole side to do so? Is it expensive?
Pretty much. Everything aft of the door is mostly one piece of stamped metal. You could scab patch the current one, but if its bad enough to need replacing, it should probably be the entire panel. The paint will then have to be blended into the rest of the car (or if the current paint is to bad or budget allows it, a complete repaint). I would expect estimates to be in the $3k range for a R&R
I just replaced my quarter panel. There is a cap load of spot welds. The good thing is all of the spot welds are hidden. If you get one make sure you whole quarter section including the inner and outer wheel house and trunk pan
I have seen it done but never did it myself. Its not a job that is as impossible as it seems at first. Yes there are a lot of welds to drill out but once they are out its not too bad.
http://www.sn95forums.com/showthread.php?69041-94-Cobra This guy did it, and took some decent pictures along the way.