You bring up a good point Serge. So what would you do? Pass on it? It's in mint condish, priced right, and low mileage. What more could you ask for? Oh yea a broken sunroof and reconditioned rear bumper cover.
The bumper I can live with since it'll be repainted. If I do get the esky and one day it rains and the sunroof starts leaking (again), I'm not going to be a happy camper..
I don't know what decision I would make Felix, but I do know this. The worse way/time to buy a car is when one has the funds, and the vehicle they've loved for a long time is available at a good price. So my only advice here, if any, is to take your time, breathe, and try to look at it stone cold.
Knowing what you know about these trucks (which is more than most people), once properly personally detached from the process, you will make the right decision.
In the end nothing guarantees a worry free vehicle, we all know that ... my personal take is that bumpers are not a huge issue as all of us knock one out sooner or later. In fact when I was talking to the body guy at my dealership he said most of them are taken out by housewives who can't cope with the size of the vehicle.
But as you know sunroofs are another thing. If the problem originates from the factory as it sometimes does, then it's never going to be fully right. They can seal and mess around with it but the cut and original fitting is simply off. Keep in mind where you are going ... Colorado has massive temp shifts from summer to winter, sometimes in one day. That kind of flexing is only going to exacerbate a root issue from the factory. On the other hand if it were a simple mechanical issue then one could overlook it.
I know you want the esky, and I know you need a truck soon ... those two elements will bring you joy when you get the right truck for you ... but only if you don't let them work against you.