Sounds like a fantastic opportunity for you here. No doubt, any manner of an alteration that wasn't done by Colt will negatively affect the value, that's just a given. However, Pythons have almost irrational "values" and it seems obvious to me that your intent if you get one is to
shoot it, and here you have a chance to get one and shoot it... which is another thing that can (or more likely
will also lower the "value."
Being that it is a Python and the marks in question aren't from some 12-year old with a jack knife or scrapes from being dragged by a truck... as time passes on, you'll still have a Colt Python, and even with the devaluing and detracting marks on it, it will be worth a lot of dough.
You're a shooter, and you want to see what the fuss is all about. This sounds like a deal you need to make!
(FWIW, I have -never- in my life handled a Python, and obviously, I've never had the chance to feel the DA trigger pull. Yes, I would love to, but I refuse to even ask someone at a show such a question. Frankly, they are too valuable for what they are for me to even want to dry fire one that I have -zero- intention of buying. ZERO. They aren't my thing.)