You might be able to save the engine, but keep running it and chances diminish. Starts fine and looses oil pressure, I would anticipate debris up in the oil pickup screen, probably your plastic timing guides. They have killed many modular engines. Depending on how long its been run and damage done the fix MAY be easier then replacing the engine with a junk yard one with likely the same problems.
First pull the pan and see what you find. If junk in the pan and pickup screen pull a couple main and rod caps and check bearing and Crankshaft. If they are in good shape the engine may be fixable. I would anticipate at a minimum timing chain assembly, phasers, Melling M340 or 360 oil pump, new lash adjusters and followers. Like I say, start in the pan first that will give you some ideas what happened.
Oh the PO344 is camshaft position sensor. Another indication you have timing chain problems. Lets hope it hasn't jumped timing and bouncing valves off pistons.
Sadly, the weather sucks and not a good time of year for any repairs unless you have access to a nice garage
Good Luck