2 prong wiring nightmare
Good news: it's fine as-is.

Bad news: Taped connections are fine IF they are either crimped or soldered. 3 wires just twisted together and taped are not ok. 

More bad news: A metal box means nothing. A grounded outlet requires a ground wire. If you have a ground wire running to the box you don't need a metal box (plastic is fine). If you don't have a ground wire then you don't get grounded outlets until you run one there.

Even more bad news: This probably isn't the only surprise the previous owner left you.