Surgery - Colorectal. In brief: Yes, most docs can. Most hemorrhoids should first be treated by conservative measures, such as bulking the stools, education to avoid bad habits like straining, sitting for long periods of time, etc.
Either system will have a burner. 23 years may very well be beyond the typical life expectancy of a oil burner, but a furnace or boiler should last considerably longer than 23 years. The boiler of my house here in MA is 58 years old and still works fine. I am starting to consider replacements, however.
Just because you called an HVAC company and it performed an estimate doesn't mean you are obligated to purchase from it. Natural gas furnaces generally last 10 to 15 years, so don't budge on getting the best furnace your budget allows. When you call for a quote, ask the HVAC company about its licensing. A suitable contractor needs to be licensed and certified to install your new system.