The value of any firearm depends on overall condition. Good finish, no nicks, scratches, rust or pitts. Clean bore. In the case of your python, made in 1973, the market has them at a very high selling price. I paid $800 for one and about $1100 for the second one. Both in nice shape.
100-1000 USD
No practical limit to the number of times.
50-1500 usd
Should be marked on the barrel
Yes
Stainless is harder.
Do a search for Jarvis. They make a bull barrel for the $597, it runs $198 in either blued or stainless.
Give me a serial number and I can help. Length of barrel, finish and grip material will help too. serial # is 72728, the length of the barrel is six and one half inches with a blued barrel and a wood grip
Resists rust better.
1864-1935
Your question can't be answered as written. What Model? What are ALL the markings? What gauge? How long is the barrel? What type of finish? Mossberg 500C, 20 gauge, 26" accu-choke, serial number K064007, checkered wood stock, blued barrel, vented rib barrel.
75-275