So my engine is done for. I am here to ask what would be better/cheaper? To rebuild it or to buy one from a local junk yard? Thanks.

Sorry to hear about your engine man nothing worse. All depends on the engine i would advise ringing a few companies to get a price because with a junk yard its all down to luck could get a grand enginen or just end up wasting money. What type of engine do you have if you don't mind me asking.

If the junk-yard will show you the test, i'd do it from them. It's easier and less to screw up I'm not sure how much it'd be to do a rebuild on one of our engines. I've never done one of ours. I know for a fact, that if you're swaping block for same block, It's a one day job with everything on-hand.

Or you could spend the extra moneys, and do a 3s swap

Kind of depends what all is wrong with your engine and how much of a rebuild/build up you want to do. If you just want a stock engine I'd say go for a low mileage junkyard engine and change the timing belt, oil pump and water pump at a bare minimum.
Let us know what happened and sort of what your money situation is like.

^ usually a pretty good idea to do plugs and injectors, as those items are usually not guaranteed. (niter is the distributors most of the time... )

go for something with warranty. i was recently selling a low mileage 7a out of a GXi i wrote off - then i came across another GXi which i've bought for a project. i swapped the engines over and she fired straight up but the headgasket was blowing slightly - good job i didnt sell it!! the gasket had gone brittle as the engine had been out of use for a while - not a big problem but if i had just bought the engine i wouldnt have been pleased. i pressume its bottom end being a 7a?