I did my 2000 earlier this year. There are two basic way to go about it. Some people modify their ESOTF transfer case for limited manual control. The better way is to swap out the transfer case for a manual version. The ESOTF version is a New Process 273, the manual version is a 271. Most of the parts are the same between the two.
If your going to convert your existing case, there is a kit for a knob that mounts under the truck or you can get creative and make something to link up to a shifter in the cab. On the 273 there is a motor that must be removed and a piece that sits behind it to determine what position you are in. The manual shift stuff will not directly bolt up but if you search around you can find a writeup. The down side is the 273 does not have a neutral position like the 271.
If swap the case, you want one off a gas or diesel truck with a auto transmission. The manual case has a different input but you could swap your existing one over. The linkage between gas and diesel as well as manual trucks is different lengths so you could modify the used one or buy a new one depending on the donor vehicle. For the 271 there is a two wire sensor at the top that you will have to wire into your system if you want the indicator lights to work.
On my swap, I used a 271 case that I picked up for $300 off ebay. The seller managed to get it in a box and send is by UPS, it's about 80 lbs IIRC. Your 273 case should go for $200-300 and the motor is good for another $60.