Andy,
Yes they do take batteries, but your's may not have them with the set, a lot don't have them any longer as they got swiped before or even after GL got their hands on them. Any two 12 volt automotive batteries that will fit in the spot where the batteries go will work...I suggest measuring the battery box and go to wally world and get two batteries with as many cold cranking amps (CCA) as you can in that size. The batteries are located behind the access panel under the exhaust pipes. The slave receptacle will be located under the main control panel on your machine, just lift the rubber flap on the bottom of the set and it should be there. I haven't seen a whole lot of sets lately with those missing.
As for the engine, it is an air cooled Onan two cylinder diesel, they used them on some civilian generators and the civilian model number should be DJE, you may even find a few references to the DJB, but the difference will be the bore size, the DJE should have a 3.5" bore whereas the DJB will have a 3.25" bore.
Make sure you check the oil and filters before you try to start it up.
I know the fuel filters should be a WIX 33113 filter, and they come with the proper gasket to seal the bowl. The oil filter may be the WIX 51004, that is the filter used on the MEP-003a but it should be the same for the MEP-002a. With that oil filter you will need to but an o-ring gasket for the bowl, that gasket is WIX 15108.
The manuals are in the resources section and are TM 5-6115-584-12 and -34. The parts TM is TM 9-6115-548-24P.
Good luck with it and make sure you post up a few pictures, we love pictures.