Buick returns
Today is a happy day. The Buick is back and all is well.
It appears that the older cars get temperamental in cold weather and the security switch in the boot often triggers the alarm. The mechanic said that’s what probably happened and the best (and cheapest) solution is to disconnect that security switch. I agreed, and it was done.
He also fixed a few other small annoyances, cleaned the brakes, did an oil change, reconnected the three horns, put all the fuses back in the right place, and it ended up NOT costing me an arm and a leg.
Best of all, the wireless door opening clicky thing works again. This little convenience makes me very happy.