Glitches and slowdowns increased, then the computer wouldn't start. Recovery partition didn't work either. Started from Internet recovery, and found that the disk was no good. Ordered an SSHD disk that was better, and only $10 more than pure mechanical.
Got the system apart, and couldn't figure out how to get the logic board out. Busted a spudger trying. Macfixit to the rescue with the guide and the right tool.
The IR sensor connector is just friction, just lever up to disconnect, and push down to reconnection. It doesn't slide over pins. The tape on the drive connector is hard to see sometimes, but it's there. You need the logic board removal tool.