"32h" refers to the number of spoke holes on the hub. Well built 32 spoke wheels should be just fine for someone your size. "700 x 30C" is a tire designation, referring to a 30mm wide tire for a 700C (622mm bead seat diameter) rim. The important number for your replacement wheels is the 700C, as using a different rim diameter could lead to clearance problems with the frame or difficulty in setting the brake pads to land on the braking surface of the rim. The rim itself can be much narrower than the tire; you'd have no problems using a 30mm wide tire on an 18mm wide rim, for example. Double wall rims are strong, as you have surmised. Machined brake surfaces are a relatively recent fashion and not strictly necessary (the machined surface makes for somewhat smoother braking at the expense of less wear tolerance), but non-machined rims aren't that common anymore.