Just stay away from flashing SBF files and you'll be fine and will always be able to go back to stock.
NB! The only SBF you should ever flash, is your STOCK SBF!
If you obey this rule, you'll be just fine
P.S. This post was written in font size 7 for a reason
and the reason is not that I'm yelling. It's just because many people here listen to other newby's, advising them to flash this or that SBF and then can't go back. It's for your own good, guys