The cathedral stands out among everything else in Togoville, so you won't have trouble finding it. This German built church has some nice stained glass and rather grisly murals inside..definitely worth a look.
Boats leave from Agbo dock when they fill up with people. I paid 3000CFA($6) for the ride, which was arranged by the guy from my hotel...you might pay more doing it alone. Be warned the boat guy will hassle you for a tip on the ride back....not all of the other Togolese passengers, just you the foreigner.