upgrading from 10.6 to 10.8
on my 2009 mac book pro, I want to be able to back up my entire 250 gb internal drive to my new 500 gb external drive, format the internal drive, and run 10.8. would I be better off running 10.6.8 or 10.8 if I only have 4 gb ram at this moment? my computer is currently backing up the internal drive using time machine. what would i need to do in order to run 10.8?
MacBook Pro, Mac OS X (10.6.8)