Matching Exisiting Drywall

I took out a fireplace and have rebuilt the wall, now its time for drywall. the wall is 14ft wide by 8ft high, it has a window on one end and a door on the other end. When I removed the existing drywall I stopped at a stud 6 inches inside the window on one end and middle of the door on the other end. I plan on using 12ft sheets applied horizonally.

My question is would it be easier to just remove all the drywall corner to corner? I worry about matching the seem from the old to the new sheets.

You want to avoid having a joint at the top corner of the door. It will crack. Do it in three pieces like this if possible

Piece one, install as a full width sheet and cut the door opening after its up.

As for matching. It wont cost that much more money to go corner to corner. If the old walls are lath and plaster or something else that will be hard to match I would strip back to the left corner as well.

Built in '92, it all 1/2" drywall. On that left side, at the window, will I need to remove some of the material on the old drywall for the joint, what I'm worried about is where the ends butt together, I don't want the joint to stick out from the wall, I'm going to have to remove material from both sides to tape the joint and get it to be flush, aren't I?

Full disclosure, I'm not a drywall pro.

yes and no. Usually the butt joints are just feathered out. I have seen people cut the paper facing so the first tape joint coat sits flush.
I would use paper tape and put a high coat on centered them a 12 or 14" swath on each side of the joint. Make sense? In other word you have a hump in the middle and then between the peak of that hump and the wall to the left and right gets filled in. That will make the mud for the joint 24" wide or more. The 'hump' is actually very slight and shouldn't be noticeable over 24" in most circumstances.

Any drywall pros care to comment on what I'm saying or maybe explain it better?

Yep, thats what I was thinking. Thanks for your help.

Been listening to your podcasts, great show.

If it was me, I wouldn't start using 12 foot sheets.

I'd use 3 inch long drywall screws to fasten a spruce 2X2 to the side of the stud beside the window, and screw another one to the studs at each 4 foot interval. The 2X2 allows you a full 1 1/2 inches to screw the drywall to so that you don't have to try and squeeze two edges into a single stud width.

Then I would attach strips of 1/2 inch thick spruce construction grade plywood to the baseboard (prolly with drywall screws) and rest each piece of drywall on the top surface of that plywood. Ensure that the plywood is a little narrower than the baseboard you intend to use.

I would use fiberglass mesh tape and I would do any seams where you don't have a contoured edge on both sides (like the one beside the window and over the door) with a curved trowel.

If you're new to drywalling, you may want to read my post in this thread:
http://www.houserepairtalk.com/f109/finish-drywall-basement-8301/

I can't even understand what you mean by the drywall "not matching up". As long as you spread the joint compound over the surface to make it smooth, the wall will look fine. If you have drywall on the wall, and you're replacing it with drywall, you're as good as on third base already. In my own building, I've been repairing 3/4 inch gyproc lath plaster walls using base coat plaster, drywall and joint compound, and it's not really very hard to do. It does take practice to get a nice job, but my post in the above thread will put some tricks up your sleeve to ensure you can do a professional looking job even if you don't have years of experience to rely on.