Until you have priced it out, you have no idea whether the economics of ground source heat pumps (GSHP) are going to work for you. But the first and most-critical aspect is to find a contractor who is actually COMPETENT to design & install them, since a hack contractor can bring even the best equipment to it's knees efficiency and even capacity-wise. In my neighborhood GSHP averages about $9K/ton, and delivers an seasonal heating-season average whole-system (all pumping & air handler power accounted for) coefficient of performance (COP) between 3 & 4 (even though best-case implemetations might be bumping on 5.) The high local average cost is likely due to a number of factors- little competition/demand, and the need to drill through granite rather than trenching slinkys into swamp dirt for the the earth heat exchange. In other parts of the US $5-6K/ton is the norm for small to mid-sized systems. Every system is unique, and the ultimate efficiency & cost falls in to the hands of the system designers, which makes it hard to do budgetary financial analyses around. (A $14K 2-ton system that runs a COP of 4 would be a pretty good deal compared to a $28K 3-ton system delivering a seasonal COP of 3.)
Air source heat pumps tend to simpler to specify and design around, but they're not issue-free either. A poor implementation can bring the net efficiency down to a seasonal heating-season COP of 1.5 or less. Ducted heat pumps that are right-sized for the heating load, on systems with well insulated well sealed ducts might come in a COP of 2 or slightly better in an NE Kansas climate, but well thought out ductless heat pumps (mini-splits/multi-splits) can average a COP of 3-3.5 during the heating season in that climate, and blow away any ducted split-system on cooling efficiency.
If you're replacing your AC anyway, the up-charge for going with a heat pump isn't huge, and with the price volatility and sometimes high expense of propane it can be worth getting off it if you can.
All worthwhile HVAC systems start with a room by room heating & cooling load calculation. Odds are pretty good that your existing AC system is ridiculously oversized for the load (particularly after you've insulated and air-sealed both the house and the ducts), likely sized with the old-schooler's " a ton for every 500 square feet of living space" kind of rule, with some extra "just to be sure". Many factors make rules of thumb like that impossible to use well (shading factors, amount and type of west facing window area, ducts in the attic above the attic insulation, etc.) but most homes with reasonable insulation levels come in at about a ton/1000' (or more.)
With a ZIP code, and propane billing with exact fill-up dates and the existing furnace's nameplate efficiency numbers it's possible to calculate an upper bound on the heat load, but not a cooling load. The room-by-room heat load & cooling load numbers will still be important for figuring out how to proceed.
If it's a fairly open floor plan a single properly sized heating/cooling mini-split can take a HUGE slice off the heating & cooling bills for comparatively low money. A ton of ductless still puts out ~15,000 BTU/hr at your likely low single-digits F 99% outside design temp, and many 2500-3000' homes of the 1990s could be heated almost entirely with 2-3 heads and 2-2.5 tons of ductless heat pump at near-geothermal efficiency for well under $10K in (unsubsidized) installed cost.
BTW: Since when is 1997 considered "an older home"? My 1923 vintage house is barely middle-aged by local standards, and I've dealt with plenty of pre-1850 homes, as well as a few pre-1800. I'll bet your house was even built with sealed double-panes, and insulation, but probably little or no foundation insulation, and ducts in the attic(?).