Next, welcome from another Ohioan or at least it sounds like you might be! Lol
Now with that out of the way, what are details of your truck? I guess first, is it an auto pr
manual trans? You would want a trans temp guage if it is auto only. No need if it is a manual.
The other guages should definitely be an EGT guage. Diesels will get hot with a lack of air. This can happen when lugging it and not building boost (more air) or when the air filter becomes clogged and won't flow enough air.
3rd gauge I have is a boost guage. Boost is a name given to the positive air pressure created in the air intake trac by the turbo. The amount of boost is a great indicator of the load on the engine. More boost, more engine load.
Engine coolant temp does not seem to be a big concern in these trucks. They have an enormous cooling system that seems to be very efficient. Actually, alot of guys put a hotter (203į) t-stat in their trucks to get them to warm up better.
Other things I would consider would be a diy air filter. Do a search on that and you will find an overwhelming amount of info. Basically, we have come up with a way to use an industrial air filter on our trucks that protect it very well. Also, consider some sort of exhaust modifying. I just cut my muffler out and welded in a straight piece of pipe. It allows the engine to breathe quite a bit better which lowers EGT's. You can also install a bigger (4") exhaust which will do the same. And last, if yours is an auto trans and it sounds like it will be hauling some weight, look into getting a trans cooler from the newer 6.0 trucks. It is much bigger and helps with the leading cause of failer with our auto (4r100) trans.