Welcome back!
That is a nice color. The floors look solid - a plus. Hopefully the rockers & sills are too.
The spare tire well looks like it has already been replaced. Looks like seam seal has been gooped around the joint. If it is otherwise solid then cleaning off the surface rust may be all it needs. The rear valance does look odd. If you are planning to do any welding yourself then a MIG welder is easier than an arc welder. It is very difficult to arc weld the thin sheet metal. Even using a MIG welder (get one with a proper gas attachment - don't bother with the cheap 'flux cored' units) you need to be careful to avoid blowing holes & warping the metal.
As far as painting the engine bay, it wouldn't need the perfection that the outer body would require, a good cleaning, touch up priming & re-spray would have it looking 99.9%. For sure doing it while the engine is out is the ideal time. Then you'll want to get in line for some of the
reproduction underhood decals that fellow BB member John M is making.