I haven't played a CoD game since the original Modern Warfare. I gradually faded out of playing regularly and had no intention of getting World at War. 
 
Then college happened and paying for a monthly online service (on top of the 50 bucks my school makes you pay upfront for XBOX live use) became an issue, so my account faded to silver and has remained for a long time. So I haven't played a CoD game online in a few years.  
 
Is getting Blops even worth it if I haven't kept up with the franchise? Would getting back into this multiplayer with the limited amount of time I'd have to play be worth the investment? I'm sure to get worked over royally in the beginning, but is it good enough to pick back up and re-learn that style of fps?

If anything Id say having missed MW2 will make codblops feel fresher than it otherwise would have. I skipped MW2 and Im having a pretty good time with the mp in this.
I even managed to get into a Zombie game for the first time, only took four days of trying! :p

Yes.

If you are really in the mood to play the current hot multiplayer game, that has lots of people playing it, then it is probably worth picking up.  The multiplayer feels almost the same, though not quite as engaging as Modern Warfare or the sequel.  If you are looking for the single player experience of Modern Warfare, this game definitely has a different aesthetic, but from what you were saying the multiplayer seems to be what you're going for.  I'm not that great at the multiplayer, but I still have found it to be enjoyable so far and basically got the game for the purpose of some online fun.  I was thoroughly unimpressed by the campaign and some of its lack of polish.