Replacing/installing a new HDD and RAM on any MacBook or MBP from 2008 onward is easy and not worth the trip to an Apple store. Just ensure you have a t6 torx screwdriver and a small phillips screwdriver.
The only real trick is with the HDD mounting bolts. There are 4 of them and a small bit of blue locktite is used on each from the factory. This may require a bit of elbow greece an your part to break free. If you start to strip the head of a bolt, stop, get a pair of locking pliers and twist the head of the bolt ever so slightly to break the bolt free. Then continue unscrewing the t6 or allenhead bolt with the required screwdriver.
Other than that, it is plug and play easy. Lots of youtube vids as mentioned above.