Welcome aboard, JCHusky77.
I was looking at the pushbuttons and the microtransistors in them have 3 prongs. I noticed on the ones that happ sells they have 2 prongs, any difference there??
The difference is that the 3-terminal version has a "normally closed" contact that is normally unused.
There is a HUGE range of attributes and quality in microswitches.
If you like the feel of them they might be worth getting.
Just remember that you can get a new Arcade Prime button with Standard Soft Touch switch for $1.20.
If there are any non-repro orange/blue Nintendo Donkey Kong style pushbuttons in good shape there are always collectors who want them to finish off their restoration. Pics
here if you want to see the difference.
The joysticks have 4 prongs.
You might want to check your count.
Should be 5 pins (right side of pic) for L/R/U/D/ground . . .

or 8-12 tabs, depending on whether the microswitches have 2 or 3 tabs each.

Should I buy an existing cab with some damage?
If the damage isn't too extensive, you have the skills to repair it, and the price is right, yes.
He also has tons of JAMMA boards, are they worth any money??
Depends on the board and whether it is working.

Pointing out that you're buying it "condition unknown" can give you some leverage on price.

Scott