A/C Button won't work

My husband has a 1998 GMC Sierra. Last year he accidently coughed some coke into the control panel on the dasboard and now the A/C Button and the Air Circulation buttons are stuck. We tried taking off the dashboard but are not able to access the control panel. We sprayed windex and spic and span onto the buttons to try and loosen the coke but to no avail. Any suggestions? How do we access the control panel?