Is that azgmperformance.com you're talking about?
EDIT: yes it is....although registering is impossible because the captcha-style thing required to register is not functioning. Yippee!
He's got around 5000 miles on the rebuilt engine along with all the mods, but I agree that a rebuilt engine is ALWAYS a concern. This isn't his first Grand Prix and it seems like he knows his stuff though. Also, I know that mods don't add value, but it's all stuff that I would plan on doing myself anyhow so why not get a car with it all done to save me some time and money? I've modded so many cars at this point that I am almost tired of doing it (mainly because of having to deal with a nagging wife).