Re: 1995 45 HP Mariner Outboard- good motor?
If the decals are original, I can tell you that it's not a 95. I have a 96 40HP and I researched Mariners decals into the ground because something seemed shady to me as well. turns out my motor was some kind of end-run which caused some confusion. 88 sounds more accurate to me but I'd get pictures of the s/n and you may be able to enhance them digitally to see better.
FWIW mine's a mariner made by yamaha, and I can't say anything but good things about that motor!
Oil injection does mean a secondary tank, though I'm honestly not sure where it'd be on an O/B. You'd have to add oil frequently, not once a yeah. It simply auto-mixes it for you, to simplify the process.