Diagnosed the problem as igniter failure and called local parts outlet. They gave me the part number, but said they were out and directed me to another vendor. When the part came, it was the wrong shape but I tried it anyway. Result - the igniter glowed which allowed the gas to flow, but igniter, being the WRONG PART, didn't ignite the gas, allowing a dangerous build-up of gas.
I then went to PartSelect, looked up the part, saw it was the correct one, ordered it (arrived within 3 days) and, because I already had the pans and covers off the oven, it was a matter of minutes to install. Works like a charm and, though I usually like to buy locally, I'll check out PartSelect first next time!