tips on replacing condenser & receiver/dryer

I have a 1991 190e 2.6 which had a perfectly functioning A/C until yesterday when a stone ruptured the condenser, spectacularly emptying the R12 charge (oh, what a sinking feeling in my stomach!). I would appreciate any tips on getting the A/C up and running again, most economically, if possible.

Does anyone see any problems to replacing the condenser and receiver/dryer with proper oem parts, adding the prescribed 20 cc of compressor oil into the condenser and 10 cc of oil into the lateral connection on the receiver/dryer, installing with new o-rings & torquing the couplings, and then, --this is the key-- taking the car to a generic A/C shop for a recharge of R12?

I'm a little concerned with how fast moisture enters the system and requires blowing out with nitrogen or R12, or is that somethiing that an A/C specialist routinely does before doing the recharge? (About 12 hours after the incident I put a bead of caulk on the hole to minimize the entry of moisture). Thank you.