Mods please change title to "anyone know a good AC guy in Nebraska" then move topic to GPC.
Seriously though, you may just need a refrigerant re-charge which wouldn't cost much. If you really do change your filter often, then it shouldn't be an airflow problem / causing your A-coil to be dirty - needing a cleaning. How is the air flow when it's operating normally? Good? Likely, not a dirty A-coil.
Bad? Depending on your set up - You could fix this yourself with some coil cleaner, a coil cleaning comb & a vacuum. If it's really expensive - get a second opinion because you're likely getting mumped. Like over $500 expensive.