A couple of Mack trouble shooting questions

I'm new to owning my own truck, and before everyone says it I know, I picked an expensive truck to fix to start out with, but the deal was right. I have a couple of issues with my '05 Mack Vision I was hoping some of you can shed some light on for me.

First, I have an ABS light always on on the tractor, is there any way to get error codes from the truck with out plugging it in to some computer? and if so how do i decifer the codes to find out what sensor is bad, etc.

second, I have a couple electrical issues which I don't know if they are tied together or common. If turn my high beams on, after about 20 seconds, they flicker and turn all my lights off until i click them off, then all my lights come back on. Second, if I am hooked to a trailer (any trailer) as soon as i turn on my ignition, the trailer lights come on even though my light switch is off, some times it's some of the trailer lights, other times it's all of them.

Someone told me the daytime running lights ws the issue with the high beams, so I pulled the fuse, but it still does the same thing so that didn't work. I'd appreciate any suggestions. I don't have any money really to back me up on this venture, so I'm trying to do what ever I can on my own so I don't drain the truck account senselessly, and still support my family at home, trying to get out of the living paycheck to paycheck atmoshere, I'm slowly starting to head towards my goal so i'd like to keep it that way.

I don't always have internet on the road, and I try and stay out 2 weeks at a time so forgive me if any of my responses are slow comming, but I will try to check in as often as I can, I like the looks of this site, it's the first I've tried, so I intend to be very active. Thanks for your time and suggestions.