I am renovating a house that I just bought and want to put in french doors in place of an 8 foot patio slider. I am trying to price them online so that I know that the contractor is giving me an appropriate price-since I live about 2,000 miles from where the work is being done. I can't seem to find many prices and I am not sure what would be best for insulating... the house is in Michigan. Any help please? I am afraid that I may get ripped off with the work since I am so far away, any suggestions? He is also putting a roof on, a furnace in and a hot water heater. How do I monitor all this and make sure that the prices are good for these things??

As for the door install, to install it should run more than 400 to 500 unless he has to replace some casing, plus the door.
As for the roof I was thinking its $135 a square to be installed. Buts that in NC
I know nothing of the funace and what that will run.
As for keeping an eye out, your going to have to trust him or take some time off work to be there,
Unless you have a friend that lives near the house to stop by every so often there's not a lot you can do. Hopefully you just didn't pic up the phone book and start calling numbers.
However if you don't live there you may not have much choice, goodluck

[QUOTE=glavine]as for the door install, to install it should run more than 400 to 500 unless he has to replace some casing, plus the door.

Yes I agree with glavine on the Install Price, some might be a bit higher and some might be a bit lower, but over all that is a good price by an experienced installer. Glavine I live in NC as well! :)

The price I quoted you is what I try and match with Lowe's and homedepot.
3ft door , 4ft door, 5ft door are all $299
6ft and 8ft are $400 to start, then extras like recasing the inside , or if you run into framing issues, which you will when you take out the 8ft slider, you'll have to get a french door that is close which you'll probably have to get something a little smaller and use a little bit bigger casing to cover the gap

I do work at Lowe's (10+ years in doors/windows) in central IL.
I checked the price of a basic 8ft steel patio door - about $1000. Labor will range $400-500.
Roof will be $41-$70 per square for materials and $100-$135 per square for labor/disposal.
Hot water heater will range $250-$400 for the unit and $200 to install.
All of the above can be done directly through Lowe's (or Home Depot). This can also be done over the phone with plastic. Both Lowe's and HD guarantee the work. If there is a problem, you do not need to get the contractor back, just call the store. Their labor is a bit higher but the convenience and peace of mind make up for it.
Furnace will vary with size, efficiency, AC unit. Price should include 5-10 year warranty (parts and labor). Range is $2500-$4000. Lowe's is generally not in the furnace business (do not know of HD).
The labor prices can all vary if there is extra work needed. This can easily happen with renovations.
Glavins comments on how to monitor are correct. Working with Lowe's (or HD) can help since there is a guarantee.
Let us know if this helps.