The heater isn't working. If I'm on the interstate, I can feel heat at the vent, but not when slower. All the lights work on the heater panel, but nothing blows (well, except for not having heat!). When this started, it would work for 2-3 days, then not for a day. Gradually it got worse until now it doesn't work at all.

I filled coolant and checked what fuses I could. I am NOT a gear head but fairly handywith tools and instructions. Help!

Take it to a garage and have them "reverse flush" your coolant system. That will solve your problem.

Also have them check for any antifreeze leaks, GMs are notorious for crummy intake gaskets; I also had a customer who had their head gasket warrantied - twice - on their Aztek.