Lower unit empty?

[Bass_boy7]

Hey guys, I bought this boat from a guy whose father passed away. The motor is 1980 evinrude 50 hp when I got the boat the lower unit was off the motor bc it had cracked and fired the bearings etc, but I was given a replacement lower unit that fits my motor in great shape from what I can see but it was given to me without the drain plugs in it and it was empty. His father was supposed to switch it all up etc but passed away unfortunately. My question is I am not sure how long this other lower unit has sat empty but it seems to work just fine when I try all the gears etc, anything I should be looking for before I fill it with oil and slap it on my motor? and is it ok that I turned the shaft to see if the gears worked etc when it was dry?