Air conditioner isn't blowing as cold as it used to...Where should I take it to have it checked/repaired?

Question

My 1998 Chrysler Town and Country has never given me a bit of trouble until now.  (I take it to Firestone twice a year for oil change and basic servicing.)  The car has 68,000 miles on it and is otherwise in excellent shape, having served me well these 11 years.

However, now that the hot weather is finally here, I've begun using the air conditioner again and am finding that it isn't blowing as cold as it used to, even when in Recycle mode.

Would you think that Firestone could get to the root of the problem and take care of it competently and at reasonable cost?

Or would you advise I take it to the Chrysler dealer (they're still in business a few towns over) and have their own mechanics deal with it? (My only concern there is the possible high cost.)

All the independent car repair shops in our community have long gone out of business, so that option is unfortunately out.

I appreciate any guidance you can give me.