Remodel 1986 Jayco PUP

My husband and I recently bought a 1986 Jayco J Series 1006 PUP. The previous owner's son had used the camper during cold weather and closed it up. When reopend the "black" (plastic) windows cracked. Any suggestions on fixing this/replacing at a reasonable cost? If removed. Netting and inside zip screen are all that is there to protect from elements.