1998 Dodge Caravan Hesitating, but only sometimes

Okay, I'm an Army wife and my husband is deployed right now. I'm having some problems with our Caravan. It sat in the garage for several months because it wasn't running and I decided to have it fixed. The dealership I took it to replaced the drive belt, the sway bar links, an electronic component that was causing the dash lights to all go out and did an oil change.

Since then (which was about a month ago), I've been having some problems with the engine hesitating. I noticed when I read the FAQ here that a lot of things can cause this. I was hoping if I gave some specific information, you might help me narrow it down to things I should address with the mechanic.

This isn't happening consistently. I can drive it for miles with no problem at all. When it does happen, it always happens between either 20 & 30 mph or 40 & 50 mph. The description of a clutch problem doesn't seem to apply though. It does not feel like it's working hard, but not going. It just lunges and it only does it when I'm applying gas. It does not do this when I decelerate.

Additionally, there is a smell of gasoline in my garage now. I don't see any leaks and I'm not losing gas, but the smell has me worried. At first I thought this might be solved by using some gas treatment (it was suggested to me that because it sat for so long, it might have condensation in the tank or something). I filled the tank and put the treatment in and had no problems driving it until I was back under a half tank.

I'd donate to you guys, but after spending so much on this van already and knowing I have to spend even more, I'm pretty much broke.