I've been modeling for about 2 years but i've never exactly touched texturing :headbang:
But to point you in a good direction here is some advice.
Realistic Metal - HDRI
scratches - bump map/ displacement (one or other although bump mapping is easier)
Texturing - You need to lay out UV's and then go into a paint program i.e Photoshop, PaintShop Pro, Painter etc. and paint on the texture. Complicated even for me but then again i've never tried....
Cheers and i hope you get somewhere :beer:
What i did was practically download every single tutorial i could get my hands on. I probably have over 10gigs of tutes
Not much help, sorry....