Good luck, and congratulations on taking on the endeavor. I hope you are also doing the header. This is the best time to replace it.
The hardest part of the job i personally encountered was installing the rear tack strip. Order a new one, because the old one will be dry and cracked, so it won't hold the staples. It has a metal channel that it is housed in, and you cannot pull it through the channel to install it. You will have to painstakingly spread the channel apart, lay the strip in it, then fold the sides back down over the strip. I did check with an automobile interior installation shop; there is no machine for drawing the tack strip through the channel.
Take lots of pictures before you disassemble, AND as you go along.
God speed.