sorry dont no anything about mame cabs must be an american thing,but there seems to be alot of people on this forum that know about this,i am guessing mame allows pc based equipment to run in a standard type arcade cabinet.
as for your transformer,you could use almost any as long as the voltages are correct but like i said try just connecting straight to mains,then if your monitor works go and get a transformer.In the uk we used 240v-110v transformers simply to get the correct voltage,but i think in the states you have some sort of law on fcc which is why you need an isolating transformer.Happ controls are the people you need to speak to for parts like a transformer,they also sell a converter for video signal but i cant remember if it converts vga to rgb or vice versa.
as for hanterax manuals they are easy to get in uk we just phone hanterax,see if you have a distributor in the U.S and do the same.