Draining and filling old hydronic heat for install of kickspace heater

mcops

I'm looking for advice/review of my thought process for this job. For a kitchen renovation we are replacing a heater in the kitchen with a kickspace hydronic heater. See pictures below. Any resources or tutorials online you can point me to would be appreciated.

I have a one pipe system. Old boiler runs on oil. My understanding is I will need to turn off and drain the system, disconnect the old heater and install the kickspace heater, then fill.

I've studied my system and have the following workflow:
1) turn off switch to boiler.
2) close valve supplying water in by regulator
3) hook up hose and open drain.
4) open bleeder valves on units to avoid vacuum

There are three drains as far as I can tell. one on the expansion tank, one on piping between expansion tank and check valve, and one on the bottom of the boiler.

The kickspace heater install should be straightforward and I plan to switch to a monoflow valve on the supply tee and there is currently on a diverter valve on the return side.

To fill
1) make sure boiler is cool
2)close drain. close bleeder valves on units
3)open valve supplying water to regulator
4)turn on boiler switch

I understand it will take some time to fill and then bleed air from all units.
My questions are:
a) Have I overlooked any steps in this process?
b) Im guessing the low valve on the boiler is to be used here, and I don't have to drain the boiler completely but drain to the level necessary?

thank you