It would be best to try to find out where it is leaking before you take anything apart. The sniffing isn't with your nose; it is with a refrigerant detector. These aren't extremely expensive, but expensive enough that most people won't want to own one. Note that you use a different detector for hydrocarbons than you use for normal refrigerants.

Replacing seals isn't a bad idea if they need it, but you should flush out the parts and lines if you're going to disconnect them.