Hi Joni,
I like the materials and the lighting in the first two renders. Just a tip on the depth of field because I think there's too much of it on the guitar neck render, make sure to use it in the way were it causes a subtle effect, it should only be noticable if you're looking for it.

Maya is quite user friendly and mental ray is a good renderer but all those nodes in the hypershade...I've used Maya for quite a while and they still have me completely baffled at times. There's just so many to learn

Nilla