I would be checking the charging system to make sure you are getting good output from the alternator. Low output will show up as quirky operation in a lot of the electronics including the tranny controls. Can't think of a connection with the gas smell. Have you read codes yet? Tranny codes will not necessarily light the check engine light. Here's how to read your OBD-I Chevy:
Troublcodes.net Trouble Codes OBD & OBD2 Trouble Codes and Technical info & Tool Store. By BAT Auto Technical