Hi all, 1st time poster here, thought I'd share my thoughts on this topic as I am currently making the same transition fro SnG's to cash. I was a relatively successful SnG player with an roi of 10%. SnG's for me is all about, playing tight in early rounds then later on it's very much a push/fold type of game (very simplistic I know but you get my point). Also your pushing TPTK on most flops.
Cash is a very differant ball game altogether, in my limited experience up to now (25,000 hands). TPTK just doesn't cut the mustard in cash and if you find yourself going to showdown with TPTK you can find yourself reloading a lot with this type of mentality. Cash games is a lot about post flop play, and your ability of reads and putting your opponents on hand ranges (something I struggle with at the moment).
You really need to become a student of the game and read up a lot on the nuances and intricacies of cash game play. It really is worth it because its so much more interesting and technical than SnG's, IMHO. GL