Priming engine oil

It's been recommended to me to prime (oil) my engine before I start it. The engine has been sitting in my climate controlled garage for 3 years. It was not a fresh build...it was a running engine when I purchased it, but still recommended..??
I bought the priming rod and somewhat understand the process with some limited research.
The engine and transmission are installed. I know I need to take out the drive gear. I've read that it should be marked someway of how it was sitting. Problem with that is, it fell out a few years ago when it was on the engine stand. At that time, I put it back in place following whatever instructions I found at that time, but not really confident in what I did then and my memory now.
(1) So, when I prime, do I need to install spark plugs..?
(2) Should I hook up an oil gauge..? (3) Should I still turn the crank by hand while priming with engine and tranny already in car..? (No starter yet)
(4) Do I have to take valve covers off..?
Lastly, when I install the drive gear, how do I make sure it's correct..?
Thanks..!!