I have replaced both front and rear fuel pumps. The only easily serviceable "seal" is that gasket (#5) between the fuel pump base and the engine case. If your loosing oil from the "drain" (called a "dry bay inspection drain"-meaning it's supposed to be dry not dripping or pouring oil) then as you say shaft seal is gone. This seal is part of the pump and means fuel pump disassembly, i.e. fuel pump overhaul. Either seal gone, shaft worn, component wobbling, etc. Quickly get into small, specialized parts (if you can get them), special tools or techniques as well as adjustments on a delicate/critical go item. Just send pump out for overhaul.
I have attached a sample picture of the engine side of the pump. Also a sample picture of pump showing drain.
After installing pump, continental has a process for setting the fuel pressures. It's some interesting reading and can be time consuming, having done it.