If things get complicated, then yes, employ the HVAC specialist for their expertise.  

You need NOT contact the other two parties at all as doing so may complicate YOUR reimbursement.

Sometimes, what seems to be simple on the outside is actually more complicated.

It's really not that complicated though unless you try and get super creative. 

Was this an upset sale or a free and clear judicial sale? 

I don't know if this makes it easier or more complicated, but our upper level may not have any gas services at all (husband is going to the property tomorrow to see if upper water heater is gas or electric, and whether washer/dryer in each unit are gas or electric).

Am I over complicating this?

Since it’s actually a little complicated, I’ll do it in steps.

I think mine aren't super complicated and I could probably continue doing them on my own but it'd be great to have someone look over my return (my 2022 one). 

If it's that complicated to learn and use this fully setup turnkey program maybe its really not that good?