I'm purchasing a home in Duluth, MN. The existing oil fired boiler has issues and needs either to be repaired or replaced. I'm considering scrapping the unit and installing an LP system, since natural gas is not available in the area... yet.

The boiler feeds a baseboard system. I believe there are two or three existing zones.

Sizing:
I know I really should have a full blown heating test done. But, for now, I'm just looking for a solid estimate. The current oil boiler is 127,000 BTU. The house is 1800 sq feet. It's a split level. The split level (majority of sqft) was an addition, added in 1984.

I also want to add an indirect hot water heater. It's currently electric. I may opt to add this later though due to budgetary reasons.

After researching online, my gut is telling me that I'll need between 72,000 and 90,000 BTU.

Boiler:
I'm leaning towards the Weil-Mclain Ultra 105. It seems to have a lot of nice all-inclusive features. It's reasonably priced too. I'm also considering Buderus and Peerless, but am open to suggestions.

My main concern with the boiler is the type. I want to make sure I'm getting the correct specs. Based on a telephone call with one contractor, I'm somewhat concerned about aluminum. He was definitely suggesting stainless. He noted issues with premature leaking and start-up leaks. Anyone have similar concerns?

I guess my questions right now are:

At the ~90,000 BTU range, is it safe to say I'm close?

Does anyone have experience with the Weil-Mclain Ultra 105 in cold climates such as Duluth, MN?

Are there other brands/models/types of boilers I should be considering?