Since you live in Portland, there is an RV show coming up in March at the Expo Center March 9-13. You should attend and see what's out there. That way you can walk through several units without being harassed by sales people (for the most part) and get an idea about the different types of RVs.
I also agree with the rent first comment. Since you are considering a truck/trailer combo, just rent a crew cab truck first, go on a road trip to the beach, and see if you feel comfortable driving it around empty. It'll be much cheaper than jumping in and renting an RV first.
