Hey, if you are already have a lot of cash experience you should find it relatively easy to transition. Cash to sngs should be a lot easier than sngs to cash. Few tips to get you started;
There's a ton of training videos available for free online. I like these guys;
https://www.youtube.com/watch?v=-k-EbmBIcvc SippinCriss who posts on here also has some excellent training videos.
Id recommend Colin Moshmans book 'Sit 'n Go Strategy'. Written a good few years ago but still has the strategy to beat sngs at micro and small stakes. The book gives you the template to beat these games and if you follow it you will be successful at the lower stakes at least.
Check out this site;
http://www.sitandgoplanet.com/
Invest in the SnG Wizard or Icmizer.