Good looking out in terms of the shop. I've dealt with people like this before.
That said, I'd start reading more DIY's on this site and E46fanatics. $800 for a VCG, OFHG, air filter, and a oil change was a complete steal. All of those if you had done yourself (painlessly simple) would have cost less than $150 with original BMW parts/proper 5w30 oil & MANN filter.