Back to the original question: What size boiler(we can give you all the necessary parts list, and places to purchase) I'm assuming a KA-6 or KA 8. The Keystoker manual gives you a basic piping and wiring diagram, and in your situation, I'm thinking you may have a heat exchanger inside the house to isolate the two systems. However considering the time-frame, that could wait for a WARMER TIME OF THE YEAR. ANY supply house will set you up with the parts, and you can do a layout on the floor while right there! I like black iron manifolds and they are off the shelf...new expansion tank, not a 30 but a 60 or 90..... I don't know who said it is getting cold where you are......it's HEATING season, pal!!
I'd be there today if I weren't buried myself. Plumbers can be mega a-holes, and this guy might be a leading candidate! This sucks when you HAVE to have safe central heating. It's Wed AM, take your manual to the supply house.....or outdoor boiler guys and they wil set you up. The wiring is straightforward, but you need it piped and filled (leak tested, too) with water, ready to fire. Have you assembled the stoker and installed the gauges, etc? Are you ready on your end to make it happen?
Don't forget to have a small bucket of furnace cement for the stoker install......and make damned sure you have have the stoker bottom in where it is suppose to be (SEEN TOOOO MANY WITH THE LITTLE ROUND KEEPER OUTSIDE THE FRAME)
Do you have the stack piped and the Baro-damper in yet? 3 screws in EACH joint..... Get off your butt and make it to the supply house. (BIG BOX stores are NOT a supply house)
Don't waste a minute, get yourself into 'launch mode'......keep it safe, no injury reports.......as you know, Shark Bite fitting can be used, so install time is minimal.. They are safe for Hydronic work to 200 degrees.
PS: This is a long one day install, and NO plumber should make it a career....and trust me, there are many excellent plumbers who would be totally ashamed of your guy. Good luck....and welcome to the forum.
Forgot the obvious: did you install any extra conduits for power and/or control wiring? Hope so.....you need a thermostat wire for low voltage control to the triple aquastat......