hey, new here at the forums. I saw the reference pic and was like WHOA HE DID A GREAT JOB!!! Then was like oh nvm, its a ref. haha =] But yea, also new to maya, but ok in C4D. Ok this is what I would do k. NURBS sphere, with appropriate isoparms (these isoparms will be the ridges.) Do as much sculpting you can do to match the pumpkin by using your side/top/front views and whatnot. Once you get he pumpkin perfect. Take those isoparms and scale them in, but before you do that you should subdivide it so that your not just scaling the pumpkin down ya know? Make sense?

(Let me know if i'm on the right track guys)

Thanks