To be clear, you have radiator or baseboard hot water heat?

Call several propane dealers for info on propane pricing and tank charge-both rental and purchase. Ask about contract pricing for a heating season.

Be aware propane pricing tracks home heating fuel oil.

At the very least, you want a high efficient system.

IMO

around here, tanks are leased. They have little radio thingies that tell the company when to come out and refill. Propane is not cheap, but I don't know if it would be cheaper than hiring someone to cut wood for you.

Is ur house a log cabin? Trailer home? Tar paper shack? My point is, who new or nice is house built? Is ur wood boiler in an attached shed? Where would u install a propane fired boiler? Do u have a finished, cement block basement? Just trying to imagine ur house construction.

You can bet your bottom dollar propane will be very expensive compared to a wood burning boiler. I would expect wood would be relatively cheap to purchase based on OP's location. Depending on age of homeowners though, it may be problematic and physically hard to feed the appetite of a wood burning boiler not to mention it's location and moving in and out of the weather elements.

IMO

Thank you all. I talked to some neighbors. We have decided to go with an upright smaller tank for now. Found out we can change location & tank in the spring. No contract, just need to use 70 gal or more a year. Hubby is only 54 but had heavy duty job for 28 yrs and has numerous back problems. House is a walk out ranch. 1/2 finished partialy underground cinderblock basement. Cathedral celings 2/3 of first floor. Built in 1977 as a lodge or vacation home as it is 5 minutes to the lake, river, hunting, snowmobile trails etc. Woodboiler is detached. I really fear the cost but have taken the plunge, we had NO heat last night because the blower died, hubby has rigged for now. BBUUURR 13 blustery degrees last night .
Thanks again for your help.

Please make sure there are no leaks at any connections. In my zone, we need LP sensors to shut off main. I have seen first hand what can happen to a condo when it's not tended to properly.