Being outside city limits changes more than who taxes the property. An acreage in Corman Park often means well water, a septic system and road access that a city lot never has to account for, and those all factor into what the property is actually worth and how it should be marketed.
Getting from multiple names on title to one sale usually starts with a grant of probate through the Court of King's Bench confirming who legally holds each share, since a listing agreement needs every owner's signature, not a majority.
If even one heir will not sign, that is a legal problem to solve before a market problem, and legal fees of $800 to $1,500 are a reasonable starting budget for a lawyer's help. Get your hand-reviewed valuation from Joel Dyck.