You can pull the blower motor and clean some stuff that way, you don't need to pull the dash. Several auto chain stores sell car-interior safe products for cleaning the evaporator.

But if it currently blows "cold", then what are you trying to improve? I'd put a thermometer in the exhaust and measure the performance. If the output temps are low, then the A/C system is okay. The compressor will actually cycle to keep from freezing up once the system reaches a low point.

If you want the interior colder and everything else is in order, then you may need to look into the "recirc" only modification.

There are a LOT of things to check and maintain if it's not cooling properly: vacuum pods, foam tube, blower motor, monovalve, thermostat, aux fan.

I think measuring the vent temps is probably the first step. That'll give a solid data point to gauge improvements.