repair an out-of-warranty Thunderbolt port The Thunderbolt port on my trusty several-year-old MacBook Pro is failing. To connect an external display, I now have to wiggle the cable around, then pull it out a few millimeters until the contacts are lined up just right. It's only a matter of time before the port breaks entirely.

Everything else about the machine is in great shape. Is this a "replace the entire motherboard" problem, or is there a better/faster/cheaper solution?
For that Mac, the thunderbolt port is a part of the motherboard (on the left, 3rd from the top): 

So unless you're able to source the parts, perform a package exchange that clearly is a machine solder and then test things, the most economical repair would be to exchange the whole motherboard. As long as there is no physical damage inside, this would be a flat rate repair ($280) for Apple and probably cheaper than buying a logic board used. The flat rate repair would fix anything else wrong with the Mac. But, if you're up to reflow that part and do advanced soldering - there are lots of people that can attempt this repair even though it's not a trivial one.