Would it be okay to laminate the original documentation such as the original window sticker to keep it from falling apart or will that ruin the value?
I would not laminate it. Instead photograph it, copy it, make sure you have a good legible copy (or copies). Laminate one of the copies to handle and keep with the car if you like, but put the original in a 'good' document protector and keep in a protected location in an environment with near constant humidity (50%) and temperature (60-70F) and away from light.
I agree, make copies and laminate the copies. Store the originals in a fire safe or another secure location.
Never laminate. Use proper methods and storage products. Call a local conservator if you have any questions. http://www.loc.gov/preservation/care/paper.html