No - just one kind (makes deciding easier doesn't it?)

Yes on applying pressure with "sticks" - you won't even need any real clamps if you have electric seats.

On your rust, I'm assuming you're talking about one of the W126 failings around the rear window. Sounds like you need to pull the window out to get to all of it. If you don't have total rust through/lack of structural material, clean up real good (wire brush, etc.) and prime & paint. I once used a "paint" on a metal toolbox that claims to interact with the iron oxide to create a new sealed surface. Toolbox is going strong.

If the value of the car is max $1000 in good condition, I don't believe you have much to lose by trying the repair yourself. If your screw it up royally, chop it and make a custom MB flat bed/pick up truck.... (did I say that?)

Have fun,
Kevin