Welcome to Allpar. Sitting on 'E'? Low fuel message on? Any 'ck eng' light or fault codes like P0463? http://www.obd-codes.com/p0463
Normally a tune up/oil change would not have anything to do with a gas gauge, but something under the hood (to or from the PCM) might have been inadvertently disconnected or cut?
If this happened right after whomever did the work, I would have them retrace their work for a possible beginning diagnosis.