If you don't plan on re-taking any social science classes in your return to school then refreshing/relearning that information is a good idea. However, when you start officially studying for the MCAT (toward the end of the pre-reqs), you should re-study the social sciences (in other words don't make this your only social science study time 1-2 years prior to taking the MCAT).
You could also work on getting your self back in school mode by taking an on-line course through Coursera (free on-line classes). I usually recommend Coursera because it is structured more like typical classes in that it has deadlines for assignments, quizzes, etc. They have a variety of courses (even some you will see in your pre-reqs taught by professors from reputable universities (Duke, Stanford are 2 that come to mind).
There are other on-line options you can use such as Khan Academy (another good resource you can use while taking pre-reqs). It is less like an actual classroom in that there is no set schedule. However, if you feel rusty (less than high school level bio., chem., and lower level college algebra/pre-calc) you may want to refresh the material. Khan Academy is good because they have good instructors who do a good job conveying information. There isn't a set schedule or order in which you have to take classes. If you feel comfortable with something, you can just skip the section.
It depends on how comfortable you feel with your current knowledge base. If you feel like you are lacking somewhere then you may want to review it. If you don't plan on re-taking the social sciences that would be a great start. This way if you forgot more than you thought, you will be able to incorporate it into your plan of attack.
Finally, if you are comfortable with your ability to study and your current knowledge base, then enjoy your time before starting classes. You are about to dedicate 8+years of your life (at least 1 year pre-reqs/MCAT, 4 years med school, min. 3 years residency depending on your specialty) to your education/training. Before you start this adventure, you may want to enjoy your time while you have it.