I have exactly the same 2 error codes on my '92 SSE supercharged, and these codes have appeared sporadically ever since I bought it in 1999. I've never noticed any driveability issues because of these codes, and I'm absolutely certain that I've never tried to start the car while in gear. In regards to the passkey fuel enable circuit error code #58, I used to get the error when the switch contacts were still wired in the steering column, but years ago I disabled that wiring and added a resistor so the key doesn't need a resistor pellet anymore, and the error code still occurs sometimes. And yes, I've cleared the codes regularly since then.
It seems that nothing needs to be done to fix the cause of these 2 codes.
On a side note, I've never seen either of these codes stored in my '93 SSEi.
'99 Bonneville SLE, white, 112,000 miles
'02 Park Avenue Ultra, white diamond pearl, 88,000 miles