Get the manual from http://www.jagsthatrun.com, then make up your mind. Buying a converted car is a good idea, but does have one big flaw:
Building it yourself teaches you a lot about the car's mechanical makeup, which, in your position would be very beneficial. But if you are not very mechanically inclined, or lack the resources, you may want to approach those deficiencies first. Building a V8 Z, or any car for that matter, is a great learning experience, as long as you don't get in a hurry, or you will get fed-up and abandon the project.
If you have a BIG cheque book, then have someone do it for you, but you will learn nothing, and probably not have it done the way YOU want it.
Food for thought!
Buy the manual for sure!
Tim