The Murcielago is built on a MR2 (mk2). To be honest im not sure exactly how much work was needed before the shell goes on as I had Extreme start the build for me. The package price is on their website with a list of what is included
http://www.extreme-sportscars.com/murci/kits.html
The build is not an easy one as with any Lambo replica although It may be possible to get one part built for not much more than the kit price. I looked at selling my own car part finished myself as I work abroad and don't get much time to try to complete the build. This option would give the advantage of being cheaper and saving you a lot of time. Finished cars often sell for between £30k-£45k so they are also quite a nice fun investment.
I would advise on any kit car purchase that all items required to complete the build are there when collected.
Here is my car more than a year ago when I last saw it