Sorry, but this is a long story. So long I have to break it into two parts. Hopefully someone will read it all the way through.
First the good. I had a gas Burnham Alpine ModCon installed in 2011 to replace a 1940's coal to oil conversion gravity system that finally cracked its block one winter. It actually limped through that last season after I epoxied the crack in the old boilers block (believe it or not that actually worked) but knew I couldn't get through another season and it was time to replace it. I let the old oil tanks run dry and started the disassembly and removal of the old system myself to save costs. I love radiant heat so never really considered anything other than upgrading the boiler.
I don't think this site had its "Find a Contractor" link in 2011 when ModCon's were still fairly new, because I had a lot of trouble finding someone who (a) was interested in a boiler instead of replacing with an air furnace; (b) knew about and was willing to install a ModCon; (c) was willing to install the Alpine (which I wanted due to substantial gas company rebate) instead of their personal choice; and (d) was willing to answer questions and include me in the planning for the conversion. I had one plumber who walked out when I wanted to discuss where the intake and exhaust vents would be placed - he seemed to be pissed that I wanted to understanding why he wanted to run a twenty foot exhaust vent in the basement instead of moving the boiler. I had another plumber who seemed gung-ho and started the work - first step was moving the water line to the new boiler location and since I had lead supply pipes in the basement that went to the boiler and outdoor faucets (yes really - the house was built in 1900 and this was original wiped lead) I wanted all the lead taken out and replaced. He was competent, but I couldn't get him to show up enough - he would come for a half a day and then leave for another week. I found out that he was doing this job as a moonlight from his full time job working as an in-house plumber at a large private high school and it was clear he didn't have time to get this job done working at that rate. He finished removing the lead and relocating the line but after that I paid him for what he had done and we parted company.
It took longer than it should have to get the gas company to run a line from the street to my house (oil prices were high in 2011) but they got it done. By this time it was getting late in the season, winter approaching, and I was running out of plumbers who were interested in the job so panic was setting in. I got more involved in the planning of the new installation and took over the purchase of the boiler and supplies. I consider myself a fairly competent apprentice plumber - I will fix drips or leaks or replace faucets, valves and toilets, solder copper pipe and valves to install a new water heater, etc. But I was never going to get involved with gas-line work or attempt a system this big by myself. But I could plan and order stuff, so I did, spec-ing out, sourcing and ordering the pipe, elbows, valves, pumps, spirovent, expansion tank, etc. I planned the new installation using resources on this site, putting in a wood wall in front of the stone basement wall to hold the relocated wall-mount boiler pumps and valves, and had all the parts ready to install.
I found a pair of good licensed plumbers who did the installation, and did a nice job. They weren't heating system specialists (I had given up on finding one of those), but they were very competent and the system was up and running right before the cold set in so it all worked out. The only thing they didn't do that they should have done, was to do a combustion check and adjustment. They left the boiler at factory setting and didn't do any adjustment (there is a single screw adjustment for the Alpine). At the time I didn't know that should have been done, and when I did find out a couple years later I contacted them, but they told me they didn't have the combustion tool which is fairly expensive and requires periodic recalibration, so I had to find someone else and let it drop intending to do it later.