It does suck but definitely do-able. I have worked full time (45+ hrs week) since graduating in 2008 and started a do-it-yourself pre-med science track taking the gen chems, orgo, physics, bios, genetics, biochem, immunology, and microbiology in the past 2 1/2 years.
Your grades certainly can suffer when fitting in shadowing, social life, family/friends/significant other, mcat studying, and all of the other little things sprinkled in that are necessary. My grades certainly suffered trying to fit all of that in and I ended up getting a C+ in both gen chems which is the reason my science (pre-med science) gpa is now a 3.3
You can certainly do it but just make sure you are absolutely ready to put in all of the work. DO NOT rush everything and you need to respect the fact that it is a long process and may experience some bumps along the way. Make sure you stay motivated too because it is very, very easy to get burned out when you throw in full time work in the mix.