At the final table, SNG's will help you tremendously. The experience of playing from one table to the winner. But most importantly, the money is tied up in the top spots, When you play SNG's you king of have to go for the win to be profitable, which in MTTs is not the case. At the final table, (since the money is generally more) people get scared and try to prolong time in an MTT and hope some other guy does the heavy lifting, the more experienced you are at SNG's, where you should be playing for the win, the better off you will be at final tables.
That being said, the steps to get to the final table. Very different, especially online. Tables are constantly breaking, you will find yourself against new players so that your image is not as important as it would be in a SNG, still important though. You will find yourself with a short stack and really have to learn the concept of (M, Abb, BB).
Also, MTTs are hell mentally, you just have to accept losing, over, and over and over and over again. All for that euphoric feeling of winning. I believe it to be the biggest roller coaster of emotions in poker.
As for building a stack, this won't be the best advice but it can help you in the short term. Observe your table carefully, pick the tight guy and just bully him to no end. Then try to bust him when you get a hand. At least your playing the player and not the cards. It's not the smartest, or most efficient, but it can work. The other way is just to steal the blinds/pots. But even with that, you are still going to need luck to go far.
This just mainly being my very very limited experience. Read some
articles, maybe even a book. Ask some of the MTT player on this site, I don't want to name names, but I will anyways, JohnnyWatford and Dakota. Don't take my advice as final, just more guideliney.