I found a guy in Aurora, IL with a vinyl cutting machine...His prices are dirt cheap because he used to have sign shop but now just does a few on side for really cheap....I will look for his name number and get it to you.. I got white letters for 2 vehicles and they were great.
Next step is to check blower inside to make sure it is running full speed...If air is moving, coils are clean, filter is new and you still freeze up, you will need a set of gauges to check further.
You got the right idea. Do NOT call for cold air again until all ice has melted... It is a common indicator of a low charge for the suction line or low side to freeze up. There are several things that will cause this but the first two you should check is air flow across the coils both outside...
Look for the return in your ceiling. If it has tabs you may be able to open it and replace the filter by standing on a ladder. If you get lucky, you won't have to go in attic.
A good friend used them and he said the quality was good but they had to reschedule several times.. He was average happy but not overly impressed.....Kind of a middle of the road review from him...Hope this helps!