Intermitten Starting Problem Anyone else have this Issue???

[J.T.]

Newbie here guys so take it easy...I just got my 2003 H1 open top 6.5 Turbo Diesel with 19k miles a couple of months ago and everything was fine until I went to Tahoe on a really cold day and it wouldnt start..called a tow truck took him about half an hour to get it turned over...drove home fine 2 hours and wouldnt start the next day...figured dead batteries...hooked it up to the charger and cranked right up..not a half hour later like the tow truck? Take it to Hummer of Sacramento they say the batteries are fine hold charge with load etc etc...get it home and its fine drive it for a week...it sits for a week still fine..then the other day I take it out park it for one day and it wont crank over the next morning?? So I hook up the charger and the Batteries test fine i try Jumpin it like before and NOTHING everything turns on fine just NOTHING when tryin to crank it...so I call up AMG Roadside and they send out a flat bed to take it to Sacramento Hummer..The tow guy tries to start it a few times and nothing...so we get it on the flat bed and when we get to Sacramento Hummer it starts right up! Im baffled by now...Tow guy says "it sounds like my starter cylenoid"??? anyways Hummer of Sacramento looks at it and calls me the next day saying my "aftermarket" alarm system (Clifford paging alarm with autostart) which was in it when I bought it a couple a months ago was wired badly that the installer only twisted wires together and used only electrical tape instead of wire fittings etc...SO I ask how much to rewire it with the correct fittings (maybe about $5-$10 fittings) and he says $380!!..anyways what Im asking is would this cause my truck not to start?? Ive installed stereos and alarms in the past and have not ran into a vehicle not starting because electrical tape was used instead of fittings..any other thoughts on why this thing does it intermittenly? ALL REPLIES ARE APPRECIATED... THANKS IN ADVANCE!!