Due to the complexity of the work, and considering your car is on its first AC cleaning, I suggest you have the dealer perform it. If you leave the AC in auto mode, chances are its pulling in outside "polluted" air. Most if not all climate control systems admit a percentage of outside air when left in auto mode. Hence your clogged AC filter, and possibly your dirty evaporator as well.

The dealer will replace all the other things mentioned, expansion valve, filter/drier, seals, etc.. Plus they will purge your system to make sure it's clean. Nga pala I remember you saying that you'll post a picture of your setting. Where is it?