Cracked rod in my 09' Impreza with 74k miles

Hey all, a few weeks ago on my way back from school my 09' Impreza that I
bought used two years ago at 57k miles currently at 74k miles broke down.  
At first the engine locked up as I was coming up a hill on the freeway and the
low oil light came on as I pulled off onto an exit ramp and the car shut off
entirely.  I was able to get it started again and drove to a gas station where I
checked the dipstick only to find little to no oil on it.  I poured 3 or 4 quarts of
oil in the car and drove it around the parking lot to see if it would seize up
again, and when it didn't I figured it would be fine to get back on the
highway(first mistake).  The car seized up again about 6-7 miles down the
road and wouldn't start back up after, so I had it towed home.  My local
mechanic determined that a cracked rod was at fault and that my Impreza
would need an engine replacement setting me back $ 5,000 for the job.  With
a functional engine the car is worth 3500-4000 according to Kelley Blue
Book, so I'm not sure if this is worth it at all.  Would running the car without
oil be the probable cause for the rod? If I replace the engine will I be able to
get another few years out of it, or will it inevitably become a money pit due to
the damage already sustained? I know these are broad questions, but any
help would be greatly appreciated.  Thanks all!