For the lower unit I think I used 80W-90. Just look in the oil section for gear lube. It's in a sqeeze bottle. You fill the lower unit by removing the plug on the bottom (actually a small bolt) and the vent screw above it. You fill it by sqeezing the gear lube into the bottom hole until it flows out the top vent then quickly plugging everything up, starting with the bottom plug. Sound backwards to fill from the bottom but that forces out any air pockets.
30W is fine for the engine. I probably used 10w-40 because I keep it around for all my small engines, but I don't think it matters a great deal.
Glad you're getting some mileage out of that motor. I had a ton of fun with it.