Well, after some deliberation I decided it was worth the effort to get the remainder of the outside wheelhouse out from between the other two panels. This was sort of a bitch.
I ended up taking a hint from some YouTube posters, and picked up a cheap air hammer. I guess they're the cat's meow when it comes to breaking panels apart.
Well, yes and no.
It worked really well in some spots, and didn't work worth a damn in others. And, as with any power tool, you can do a lot more damage in a lot less time. I'll have to do some repairing, but in the long run, it will be for the best. And hopefully, I'll do a better job on the other side. I can see how the air hammer can be a great asset--I just need more practice.
I began fitting the inside wheel well. It's going to be a bit tricky, because I'll have to fit it and the quarter panel at the same time, more or less. But then I can clamp the wheelhouse in place and take the quarter off for welding.
I still need a punch tool. Trying to decide to get a hand punch, or a punch/flange tool. I'll probably just get the punch/flange tool, since I can use it for other stuff down the line.
One thing I think I've forgotten to note is that I also have to repair the rocker where it meets the wheel well. This should be a simple patch job, as all I've got to do is box off the end and blend everything in properly. I will likely get in there and do some rust treatment on the inside of the rocker while it's open.
So, it shouldn't be more than another week or two before I have this side back together.
OH, one more note, I think I will go ahead and replace the trunk drop while I'm at it. Might as well. The old one is usable, but it looks pretty bad, and my hammer/dolly work simply isn't up to it.