regarding "buying and not building"
...I'd have to agree.
It'll take a very long time to build a well sorted-out car. At the end of it all you would never be able to sell it for what you think you might be able to. There are many E36 325i Jstock, JPrepared, and SCCA IT cars out there. Another gentleman that you might want to look up is Xavier McClure. Very nice guy, he has been racing for YEARS and recently moved up into the realm of the E36 chassis. He's extremely mechanically-ept but decided to just buy a car that was already built. At that point you might only have to redo seat mounts, replace harnesses, brake job, maintenance, etc.
Just my two cents.