not sure what to tell you with the brake booster, but for the engine mounts,it doesn't really matter, we're not talking about precision parts here. For my BMW, I buy my parts from BMAimports (www.bmaparts.com), and they carry volvo parts too. Theyre all OEM, and have good prices. To replace them, You'll need a floor jack to lift the engine.

As far as the seals, you may want to replace the camshaft seal and timing belt all at once, but there is no reason to replace the shaft itself unless its been taken out, measured, and shows signs of wear. I cant say that doing all of that is easy by any means, I would recommend you look over the procedure before you buy the parts to do it yourself. Send me an email if you have any more questions- volvo240@ufl.edu

-Dan