Pull a panel and see how well it lets loose. Pulling/drawtight/guardz and skimming is a good option, however can be a daunting and overwhelming task if the paneling pulls hard. Not sure how skilled you are but Ive seen plenty of situations like yours go south because of skill limitations....new rock will give you consistantly better quality, but if you are confident enough in your taping/texturing skills skimming is a viable option. Keep in mind drawtight or guardz may not completely lay down all blisters the first coat and you will more than likely be cutting around these spots after your first skim, all depends on how easily the panels pull and how much paper is ripped off the rock.