Getting Serious--Need a mentor for the submission process

The novel is complete and revised and polished. I had help from this board on the revision process (big shout out to Yeshanu). Now I need help with the rest of it.

I've subscribed to Writersmarket.com and I've started looking for agents. I basically need help crafting and polishing a query letter and creating my synopsis, as well as looking for potential agents.

One quick note, because I noticed mammamaia mention there are some sorts of things she won't work with, for example, and I don't know if other people have similiar policies. It's a murder mystery with scenes of explicit violence, sex, and violent sex. NC-17 and all that.

Anybody with any experience is all is appreciated, because no matter how much experience it is, it's much more than what I've got.