Should I Rebuild or Buy???

I just bought a 1979 F250 that is mint. Only rust is a tiny bit on the cab corners, runs great, interior is mint. It's supposed to be a tow vehicle. It's got 132000 kms on it. It was sitting for a few years before I bought it.

I take it in for an oil change when I get it, they say it runs great, engine is great, good deal blah blah.

Starts to run a little rough, then really bad, about 250km after oil change. No oil around engine block, none underneath, doesn't burn any, no smoke nothing. Check the dipstick and it's bone dry. This is <300 km after oil change. I'm pissed, think they forgot to put oil in at the shop. Engine now has a tick that it didn't before. Take it in to shop to say WTF and they say they filled it, it's blow by. Sure enough you rev the engine and raw oil sprays out the tail pipe (which they didnt' notice when they inspected it).

They say only recourse is a rebuild.
So, what do I do? Is it really time for a rebuild?

A) pay some guy to rebuild my current engine for 3-4K???
B) Buy a rebuilt engine (just saw one online for 1400 USD)
C) Rebuild it myself with help (I'm a girl but I'm pretty smart and my dad has a shop I can work in). How long would it take??

I fefel like a sucker, but it ran so good and was so much better than all the other trucks I looked at. It was the only one not leaking like crazy (so I thought)

the cheapest right way of getting you back on the road is to buy a kit out of P.A.W. you can get everything including crank for $791 now now this is only cheapest if you have some experience if not i'd say buy a remanned engine from your local auto parts store with a warranty. now the 460 can become a true performer for 3-4k. the engine rebuilt in stock form should only take a couple weekends to rebuild. to make a long story short i would say it's time to upen it up and see the damage as for which route you take it would be up to you there is a lot to be learned by doing it yourself and the pride goes a long way too. myself although i've had my runs of bad luck i still do all my own work that way i'll have noone to blame but me. hope i've helped.