You are going to be talking about thousands to do it properly (ie safely!) if the chassis is bent, and this is not something you want to be doing as a diy project.
I'd strongly advise against driving it until you've had a body shop look it over.  May just be the rear pan, but if it is more then the handling will be potentially unpredictable, and any further incidents could see you driving a concertina......
Why not just claim off the person who rear-ended you, break the car for bits, and buy a new project with the cash?  If you've already done one project another will be easier.
Lots of cheapies around in the winter- go on- treat yourself!!
