Congratulations! They are fun trucks to drive (and to work upon...).
Since ACE didn't say it: Get the manuals...
Best deal is the 3/4 ton CD set from Military Media (about twenty bucks) that has all the M37 manuals on it so you can print out the pages that you need while working on an assembly and save your reprint manuals for reading in the throne room...
Meanwhile, in addition to the Michelin 1100r16 and 900r16 tires that are loved but that are getting very hard to find, Yokahomma makes a radial that will mount up that performs well. For bias, in addition to the aforementioned STA Superlugs, folks like to run the Power King Super Traction/Co-Op Grip Spur (tire is made by Kelly Springfield division of Goodyear and has many brands/names depending on who is marketing it), as well as NDT's (if you want the orginal look and don't mind relatively poor performance on wet pavement).
Tire and rim info can be found on my website.
http://www.garbee.net/~cabell/tires.htm
As mentioned above, the correct hot water or gas fired personel heaters that are mounted on the driver's fender are getting pricey. They also restrict access to the distributor, generator, and starter since they are mounted on the driver's side of the engine... A lot of folks use the M151 heater and mount it under the dash, a buddy uses a commercial truck/equipment heater that he mounts under the driver's seat.
Info on installing a M151 heater can be bound on my website (three different instalations are documented...).
http://www.garbee.net/~cabell/heater.htm
Brakes are relatively easy, rebuild is covered in the manuals. Consider converting to a dual MC. Also consider going to front wheel or four wheel disc brakes instead of rebuilding the stock drum system. More braking power, less maintenance, and much less expensive consumables down the road (GM 3/4 ton pads are a lot cheaper and easier to source than the Dodge shoes...).
Info on these conversions can be found in detail on Ray's Uglytruckling site (he's the guy who fabricates the disc brake conversion kits).
http://www.uglytruckling.com/M37 Trucks/M37 kits.htm
As you may have noticed, part of this is just a shamless plug to say that I've got some info on my website that might be of use to you... For the rest, just ask and we'll all try to help...
Enjoy.