Sound good! That back seat in a Prostar isn't for folks that don't like water
I think there are three places to lubricate the steering. Two on the cable and one on the rudder. IIRC one of the cable fittings is just a port, not a zerk fitting and grease will also escape from this when turned fully one-way (don't remember which way). You might disconnect the rudder and clean/grease it too for good measure.
Good links on steering/rudder:
Note the picture with the grease oozing from the overflow port on the rudder - if you don't have this, yours could be caked with old grease.
With the cable disconnected you might be able to distribute the grease in the steering cable a little better.
Congrats on your work so for - great looking boat!