buy a diesel car and convert it to run on used vegetable oil

Mu husband Mercury Man got a new (ok gently used) car and our daughter I-bop’s car is shot (she got a car from the parents of one of her friends for free, but the engine cradle is about to fall out) so we’re going to trade it in for parts and get her a used car so she can get back and forth to college and work. I wanted to keep it and then make this the car we convert, but the cost of a new cradle and install is prohibitive. Which leaves my car, still stuck in impound (you don’t even want to hear about that, long story). It’s an old car and got a few things wrong with it, nothing major, but busted enough I won’t mind getting in there or be scared I’m going to damage it irreparably. I found instructions! and I’m going to get started next week when I get my car out. Seems pretty straight-forward:
http://www.ehow.com/how_2004136_vegetable-oil-fuel.html