how do i change a serpentine belt on a 2004 ford taurus 3 litre sohc with A/C.

It is best to gain access through the passenger side wheel well to do this job. You only have to rotate the tensioner to loosen the belt to take it off. Then reinstall it on all of the pulleys but the tensioner, rotate the tensioner and slip it back on. Here is a diagram of the belt routing.

how do i gain access through the wheelwell? Do i need to remove anything there? What tool do i use to rotate the tensioner?

You may have to remove the inner fender cover to gain access. I can't remember if you use a 3/8 ratchet itself or if you need a socket to go with it. I appologize but I haven't changed one in a while.

What is I dont have an AC in my car. Do I have to install one or can I bypass the pulley. Do I have to get a different size belt for this if I do bypass the pulley.

What is I dont have an AC in my car. Do I have to install one or can I bypass the pulley. Do I have to get a different size belt for this if I do bypass the pulley.