Does anyone know if you can get married here? And if there’s a price!

Yes you can!

I have been to a wedding where there are wooden seats.

https://www.dsm.city/departments/parks_and_recreation-division/permits_and_reservations/wedding_venues.php Looks like it is $150 reservation fee.

You can, I've seen people get married in auditorium. You would probably need to contact Des Moines parks for reservation