Stop in for a cup of coffee

It’s not the original tank, and it looks pretty good from the outside. Just figured it’s likely got varnish in it from sitting
So you haven't run it yet? If not, maybe back flush the lines and suck out whatever is in there. See what's on the pickup screen....
If it's all clear, nothing to worry about. If not, get a look in it and decide where to go from there. But you will need to slosh it around to do much cleaning and not gonna do that without dropping the tank.