Ebay LM7's
I will buy small stuff from the bay but a used engine? Nah.
Speaking of local yards, there are some in my area that think any used engine must have gold pistons and there are other yards nearly giving them away. Honestly it took a bit of searching but I found a place with reasonable prices and what I wanted in stock.
I say try to get it as complete as possible - small stuff (sensors, harness, PCM, etc.) will kill your budget and any surplus you have can be potentially sold to someone that needs it.

...and for transport, I borrowed a friend and his truck - then fed him lunch and paid a few $ for his time and effort.
Most sensors interchange freely with practically any later GM engine. V6 or whatever, so small sensors/connectors are a non issue
I would recommend you do the normal used engine inspection and pre (new oilpump, valve cover gaskets, etc). You wont get the wool pulled over your eyes unless you let it



