I have a 96' aurora and would like to know how to retrieve trouble codes without a special tool...... and how is it possible to reset your service engine light if possible at all?

Since you have a 1996 which is odb-ii you will need an odb-ii scan tool/scanner to retrieve diagnostic trouble codes (DTC). Also, a a scanner will clear DTCs and reset the SES light. Of course repair action should be taken first before clearing any DTCs.

Go to a Autozone or Advance Auto Parts store. They will read your
codes for free.
If you then purchase a part from them to correct your problem or problems
they will clear the codes for you, after you install the new part.