Roadrunner, roadrunner

So two days ago I noticed a dark spot underneath my parked car, about the size of a football or so, I took it last night to the Instant Oil Change place which checks and fills fluids for free.  I mentioned the possible leak to them and they found out what it was right away:  transmission fluid.  Super.  They didn't sound that concerned, said it was a tiny leak, and my transmission fluid was actually full.  But it still worries me, because obviously when the transmission goes i'm screwed, replacing it would cost more than I originally paid for the car.  I've only got a few months to go, but I drive a ways to work everyday, and plan on going down to Chicago at least a couple times, not including the final move.  I'm going to go this weekend actually.  And my transmission's bad enough already, at certain speeds it lurches wildly (especially when i coast down to around 50-55 mph, i nearly get whiplash sometimes) and never smoothly accelerates.  I don't really know what exactly to do, i'm going to buy some fluid and one of those long stemmed funnels so i can check it halfway to chicago, making sure i haven't lost a quart on the highway.  Maybe i'm overreacting, but this is all too dramatic for my tastes.  Another couple thousand miles is all I'm asking for here.  That's not too much.  After that I'll walk to the grocery store and take trains.