Ok, I can answer a little bit.

On difference between MTTs and SnGs, is that you will be playing at a full or nearly full table for much longer. If you play a typical SnG strategy, you don't play many hands until the table is short handed, then start playing aggressively.

You won't be able to do that in an MTT. You will have to play a more even game and play position and blind steal.

Marm can probably answer the re-buy specific questions, and hopefully KidRed will have some good insights.

Re-buys can be pretty crazy, with people raising all-in with 56s pre-flop and crap. Also, the blinds structure will affect your play. If the blinds go up quickly, you will need to play much faster to avoid getting blinded out.

All my expirience is from on-line tourneys though.