You don't have to estimate anything. One of my suggestions about 187.2 posts back had suggestions of how you could do it. You can weigh the truck, trailer and everything that is carried in them. Even if you dont own the trailer you can mock up what you would take with you and weigh those items. You can look at others lists of things to remember and come up with those weights.
For example pretend that one you are going on vac for a week or two and gather all the things you need to take. Weigh them with a bath scale or small scale. Yes it all may seem like a pita but thats just the way it is. If you dont want to teach your self you will suffer in the end.
Also write down the handles of all those who not only said that you can pull 3500 lb, but wanted to pm you with uneducated advice and see if they will contribute to transmission repair or total rig replacement and hospital bills if you lose control of it.
Listen. Take notes. Make lists. Read. Visit campgrounds. Talk to others. No substitute for educating yourself. Depending on others is like cheating in school, you just screw yourself.
