Chris, get the basement done. Domestic harmony is paramount. I repeat, domestic harmony is of the utmost importance.
If you have any free time, wear the correct clothing and work in the cold. If you are not working with liquids or fire, a couple layers of cardboard from an appliance store will be a great insulator if you need to lay on the ground.
A couple building tips (not just for Chris's garage):
1. Spraying foam insulation is a professional endeavor. It is a great way to insulate but it can be costly. Structurally, it has the same effect as strengthening your building as a sheath of 5/8" plywood does. After installing foam insulation, let the building air out for as long as you can (several days/several weeks).
If you use small amounts of foam (sold in aerosol cans) make sure that you allow it enough room to expand. Using too much around windows will keep them from opening and is a b*tch to remove.
2. When installing fiberglass insulation use a good quality mask/respirator. The body has a tough time removing tiny fiberglass particles from the lungs. Cover the insulation with drywall or plywood. Heat rises so your best bang for the buck is using a greater R-factor insulation in the ceiling area.
3. If your garage is attached to your house put two layers of 3/4" drywall on the wall separating your house from the garage. In many places this is in the building code. This is a relatively cheap way to isolate your house from any fires that might occur in the garage.
I am currently in the process of putting up a 32' by 64' shop. It is a used metal building that I bought from a friend for the price of scrap metal. He needed to get rid of it and I couldn't resist. Of course, I couldn't just put it up as is. By doing so I would only have had a building for cold storage. So I am using the steel girder/truss system for the back 40' and the front 24' will be stick (2" by 6") construction. Having used foam insulating on other projects, I am sold on it. The entire building will be foamed. The front 20' of the building will be enclosed work space. The back 44' will be somewhat "cold storage" (just above freezing) for vehicles, tractor, etc.
This is truly a dream coming true for me. Dump truck, tractor, implements, etc. have always been outside and have suffered. I have also been paying on storage in town for the '39 Ford, my mom's restored '80 T-Bird and a beautifully restored complete Model A chassis that I will probably sell. I also have a pretty nice '28 Phaeton that will need its own place (in the front 20'). In other words, this building will be full at the moment of completion.