Go slow and use proper sized tools to avoid screw stripping if your changing levers.
Don't ever force anything. For buttons, remember the grip tabs are plastic and while flexible, they will break if you are rough with them.
Focusattack, arcadeshock, and paradise arcade are all great shops.
You may also find a deal in shoryuken.com's trading forum and definitely review the fans in the tech talk forum. I'm has pretty much all been done before and just about nothing is fatal.
Actions (Abxy or square tri cross circle) are 30mm, start/select/options are usually 24mm.
So you're right on track.
Thanks. Would I need any other tools aside from a screwdriver? The button connections can be (dis)connected with your hands, right?