05-31-2013 11:10 PM
You should first prime the walls with a dedicated primer which will give the finish coat good adhesion. Glidden's Gripper, Behr's #75 or Zinnser's 1-2-3 are all great on vinyl surfaces. If you intend to use a strong color as a finish coat, consider having the primer tinted toward the finish color. This will possibly save you having to do two finish coats.
You certainly can texture the walls. You should still primer the walls first to assure that the texture will adhere, and then primer once again after texturing to seal in the extremely porous texture.
Do your walls have the little "batten" strips that hide the panel joints? If so, these can be removed and replaced with fiberglass tape and drywall compound, much like drywall taping is done. Taping the joints will give a much more "finished" look than the batten strips. If you go this route, do your general priming first, tape the joints, and then spot prime the seams after sanding them smooth.
Hope this has helped.