As Zebra stated, it depends on what engine you find and for how much.
After a trans fire burned up most of my wiring harness along with cooking the trans, I decided to go the LS swap route than finding another trans to back up the old tired 350 Gen 1 small block. My engine was also developing a rod knock so this seemed the best route. After scouring Craigslist, I scored a '99 6.0 with all the harness/PCM along with another transmission for $750. I sold the old engine for $150 and the burnt trans for $50. I bought a new radiator, engine mounts and other incidentals and still wound up spending just under $1000. If you have the time to shop, the deals are out there.
'93 Chevy 1500 4X4 ECLB with a '99 Silverado LQ4 6.0 and '99 Escalade 4L60E. SOLD IT!!
New toy: 2001 2500 HD 4X4 Extended Cab Long Bed
John