The Radeon HD 8550G is much better for playing games than the Intel HD 3000.
Note that to get the best performance out of the Radeon HD 8550G you need to install another stick of RAM so that the RAM works in dual channel mode rather than single channel mode. Otherwise, you may loose around 20% - 25% of performance; just a guess.
RAM should be fairly simple to install. You can either buy the RAM from Newegg or buy the RAM from Best Buy and have Geek Squad install it for you. I would guess that Newegg is the cheaper option.