well lets break down the model number for you
GL C 025 U A S071
GL = Fuel Type (LP Gas)
C = tires (cushion)
025 = truck capacity rating (2500lb)
U = engine type (mazda UA series)
A = Transmission type (Automatic)
S = Mast type (Simplex) single stage FFL
071 = Mast retracted or collapsed height (71in)


Now as far as that tube on the side of the engine?
It is a vent tube for the crankcase, if your getting water out of it that is just condensation that usually happens when you only run the lift for brief periods, the temperature change causes the condensation to build up and if you don't run the engine hot for longer periods it does not evaporate. Eventually your engine oil will start to look almond color because the water will make its way down into the oil pan and get mixed up with the engine oil. If you see this happening you should change that oil and filter and not let it run like this long, water is bad and can scar the bearings in the cam and crank and other parts like the oil pump, it will make them wear out faster.
Also keep an eye on the coolant level, if your having to add it periodically or even frequently and do not see any on the floor under the lift then you may have a head gasket problem and this can also lead to milky looking engine oil. Remove the oil filler cap and see if it has a build up in it, if so clean it up.
When you change engine oil make sure you use an HD (high detergent) type oil so it will clean out all that gunk over time. DO NOT use any of those 'seafoam' type addetives in it, that will ruin the engine and you'll be pulling it and rebuilding it before you know it. It would be best to just let the HD oil do its job over time but that will require you to have to run it alot more so it can. If you do not run it much then it would be best to just leave it alone and just do your engine service on it as you normally do.
As for engine parts? I think you can still find them through yale, and also NAPA. (ignition parts, thermostat and waterpump and probably gaskets too).
Hydraulic parts like seals you'll be limited to yale or if unavailable there you have to resort to a hydraulic cylinder repair shop, if they are reputable then usually can find or match up seals for cylinders.
Now as for the transmission it probably tells you on the dipstick but alot of the older ones used Type F or Dextron fluid. Over the years the transmissions evolved and the fluid was upgraded to Mercon/Dextron III, (synthetic based) and today Mercon or Dextron III is used and should be compatible. If i remember right those trucks used Type F so you would use the Mercon.
Now if you are looking for books on this good luck with that, you'll only find those if someone has an old copy of one and is nice enough to scan it for you. The mfg only keeps most recent models in their database, these older models were purged off the system a while back due to the age of the machine.
UFF.... this new forum format isn't parsing anything right, its jumbling it all up in one continuous paragraph. I'll have to let admin know, sorry man