Solar:
Solar is a wonderful thing, but PV panels are not cheap, nor light or aerodynamic, so I really don't think they belong on a car unless you are in the middle of NOWHERE. People have done some amazing things with solar and cars, but I don't think it's the way to go for a starter project. Electric outlets are EVERYWHERE! (Wait til X-mas and just look to see where all the lights are plugged in!)
Heat:
Heat in an electric car is a big concern of mine. Even if I am wearing gloves and a coat, the windshield MUST be clear and viewable. I think I will install an electric heater unit in place of the original ICE heater. This will be mostly just used as needed for a defroster.
You could also have a standard electric space heater in the car set up on a timer, so it kicks on for a while in the morning before you hop in the car to leave. Then your car is at least nice and warm to start with, and the electricity comes from your house instead of your batteries.
Cheap:
I am trying to do my conversion as inexpensively as I can. It seems like the keys to this are: be patient, wait for deals, find GOOD used equipment, and talk to lots of people.
I would also highly recommend looking through all sorts of the electric vehicles at the
AustinEV site.
There is also the EV discussion list and
DIY Electric Car Forum
and lot of other interesting places on the web to visit.
Hope that helps!
-Ben
PS: You will LOVE electric! It is SO FUN!