You don't normally plaster over drywall. Are you saying the joints have not been finished?

What reason did your drywaller give for wanting to replace?

If it does need replacement, there is usually no need to remove -- just hang new board over the top of the old using 1/4" or 3/8".

I have some of that old drywall in my house and it has a much heavier "paper" than today's drywall. More like cardstock. Were the seams ever taped and mudded or we're they left uncovered all this time? Are the edges flat iron curling? Damage?

I know when we remodeled our living room we took down 70's paneling in the lower half of the walls and replaced it with drywall. We were able to get a good seam between the old and new...I'm sure we did a lot if tapering and a skim coat on all the walls though.

Thanks PPF/Rachel,

what i meant was the seems werent mudded. Rachel i dp yhink it is drywall panel tgat has that heavier card stock, and it doesnt seem in good shape, they started mudding tue seems in certain areas and just left it partially done. Here's a coupla pics:

Who is mudding it? The Dell dude?

I am not a drywall pro, but here is what I see:
-whoever starting mudding the seams didn't know what they were doing.
-the other seams are in decent condition
-it looks like the drywall is flush with the trim around one door so putting new drywall on top would look horrible.

Other things to consider...if your garage shares a wall with your house a contractor may have to take new code rules in middle if he starts messing with it. I believe it would then have to be a certain thickness for fire prevention.

I would just ask a contractor about options and reasons why or why not to either mud and finish the seams and paint or replace.