Can I pull my own wire and install outdoor coachlights on my garage? If so - how?
From your question, I would guess that you don't know a lot about wiring or electricity. There are good books at homes stores on residential wiring which give the basics, wire types and reasons, box sizing, etc. They do not cover local codes. Most areas allow live in homeowners to do their own work, but it must meet local code and be inspected. As suggested, what you want to do could be easy or difficult, depending on the construction.
If you want a very comprehensive book on the subject, get "Electrical Wiring Residential", by Ray Mullin His 16th addition is referenced to the 2008 NEC. Available on line or in book stores.