'05 - Simultaneous malfunctions (p.s. DIC, speedo, t/c, no shift)

Have an '05 Cobalt LS we are planning to sell, but want to try and diagnose an intermittent problem first and not stick the new owner with a surprise. I found a couple similar posts, but thought I'd check for any new suggestions. The problem(s) only pop up occasionally, sometimes several weeks, or months, between.

One issue, that to my knowledge has only happened once, was as my daughter was driving home from school it apparently just died and she coasted off the road. Fortunately started right back up and she continued on.

Repetitive problem, again only occasionally, is when shifting out of park, the transmission goes in with a "clunk", DIC displays "power steering", and T/C light comes on. I've come to realize I can drive away with no noticeable effects, and the DIC message clears, as does the T/C eventually. May or may not leave the "check engine" light on, but that too usually clears itself after several starts.

The latest incident recently occurred after driving the car for about an hour and parking it with absolutely no issues or messages. I came back to leave and upon shifting out of park experienced what I just described in the previous paragraph, but this time as I started driving also found that the speedo wasn't working, the outside temp showed --- in the DIC, and eventually realized the tranny wasn't shifting out of first. Was looking for a parking lot to pull into, and all of a sudden the power door locks automatically locked, and everything started functioning normally again. Continued on without having to stop, ran fine. The "check engine" light did NOT come on.

Have seen mention of wiring connections, VSS, etc. Any specific suggestions of a harnesses/connections to check, or location of VSS, etc. would be greatly appreciated. Hate to invest hundreds just prior to selling it. By the way, power steering motor was recently replaced under recall.

Thanks.