2619 Behind V6 Silverado - and Altitude

I'm considering a Trailmanor - the smallest one, the 2619 (with A/C). I'm a little worried that it's still more trailer than I'll feel comfortable pulling. I want to know if my fears are well founded or not.

I have a 2003 Silverado 1500 with the small engine - V6 4.3L. It's got the 3.42 axle. I'm not worried at all about staying under weight limits of the truck - the truck can pull 4900 according to the manual, I don't think GCWR is going to be an issue, and I travel light (seriously - usually it will just be myself, no passengers, empty water tanks, etc). I do tent camping now and I do that with one tent and one (largish) bag.

I live at high altitude, about 7500 above sea level. So I know my truck is not running as well as it would at sea level. I also know that I can climb any hill in fifth gear in my small Ford Focus anywhere east of the Rockies - but I can't do that around here - not because the hills are steep, but because there is no air for the engine. So I'm most interested in experiences at high altitude, as I think driving this rig at sea level (or even a couple thousand feet) will be like driving a sports car compared to what I'm used to - that's sure how my Focus feels with it's puny engine.

I'm not worried about safety on this - I have no doubt with the right hitch, brake controller, etc, that the rig will be stable and able to be stopped. I also have driven hundreds of thousands of miles in pickup trucks, so I know they don't drive like a car, nor do I expect them to. That said, I have done very little towing, so that's a new area which will take some practice. Of course if someone thinks I'm wrong, let me know. I'd rather have someone disagree with me then end up dead!

Basically, when I go up some of the hills around here, am I going to be going up them at 20 MPH with black smoke belching behind my truck, or am I going to be able to make up the hills at a comfortable speed (50+ MPH)?

I also do a lot of trips east - I'm assuming that I shouldn't have any problem keeping 65 or so on the flat areas east of the Rockies (slower when conditions dictate, of course).

So, should I just ditch the idea of pulling a TM with this vehicle, or am I more scared than I should be? I of course plan on talking to some dealers about this, but I also think they might have a tad bit of vested interest in overselling my tow vehicle!