I have used them in the past, with limited success. However from reading and listening on this and other such forums, I do not think they do much for the Dodge/Cummins combo. Yes a shift kit is very cheap and would be nice if it solved the problems. Believe me I think if it was the answer you would see it listed in every signature of a automatic owner. But you will not find it listed. There are many problems associated with the diesel/automatic combo, shifting is not usually listed as one of the complaints. As amatter of fact I think the trany does a fine job, it seems to be strong enough and mine never had a shifting or hunting problem. The big culprit is the Torque converter and it's in-ability to hold the torque. There are three major issues I see :1. stall to high, 2. not enough friction surface to hold torque, and 3. low line pressure. This is over simplified, but highlights the trouble areas. In the trany the use of a modified Valve Body corrects areas of pressure,shift points and lock-up. All in all the transmission does very well for a 30+ year old piece. I believe it's is obvious that Dodge has used this transmission for much to long and a modern trany is much needed. I can't help but to think they know this and are hard at work to resolve the problem.
Getting back to you and your current needs, I am afraid there is nothing available that will fix the autos problems cheaply. It is for the most part something that is only done when all other options have run out. And at the tune of around $4,000. 00 .