It's a little misleading...the main post office for Overland Park is right off Shawnee Mission Parkway/Metcalf (which would be about 7 miles) and all that's there was a really old Holiday Inn. The Marriott etc is at 435 and Metcalf which is closer to a 20 minute haul from SMPky/KS 7

Better would probably be Lenexa (roughly at I-35/K-10/87th St) where there are some options and you're a little closer than far west on SM Parkway.

Overland Park is a big place which sprawls. That said, traffic moves...