I've never heard anyone say they had too much cooling for an automatic transmission, in tank plus another is a good plan.
The best advice I ever got about lining up panels (I suck at it too) is to do one thing at a time, and start at the back moving forward, quarter panels and rockers don't move, so you have to do your best with the back and bottom of the door, then make the fender fit the front of the door, and hope you don't end up with giant gaps - or contact - at the hood.
Tape off the edges and use paint stirring sticks and like to hold gaps where you like them as you snug up the bolts.
Walking away often to build patience has always been required for me (I've only done it a few times)
- this is one of those things that can drive an ordinary man completely insane! It looks good in pictures already!