@joshc is that worse than mine was before cleaning?
Worse I think. But... the battery damage in the pics above is not the worst I've ever seen.
4MB should be enough to get started.
Yeah 4MB is very decent especially for System 6.
The PSU is an Astec AA15830 it looks pretty grotty but I haven't delved inside yet.
There are other options you can explore later on, if you decide you don't want to repair the Astec unit. I put an ATX PSU inside the original enclosure before.
The floppy drive is full of fluff and dirt. It looks a pretty flimsy affair with only a plastic sheet instead of a metal case. I'm not overly impressed with Apple quality considering how much this thing cost when new.
It appears to be missing the metal shield/cover around it - someone must've been lazy enough to not put it back on. The Sony drives are really high quality and are good drives, when they work.
So in this pic:
Those capacitors, and the logic gates next to them, and those diodes, form part of the startup circuit. This area around the battery does need to be repaired in order to get the machine to start, at least if you want soft power to work.
I might be stating the obvious here - but replacing the HC132s and HC74 and diodes with new components is going to be the way to go - the ones on there look toast.
what to do about the battery holder?
Remove it, and keep it that way, unless you are bothered about the machine keeping its own time. There are other ways to get it to keep time without the battery though. The battery is not needed for the computer to work.