As an owner of a 2000 Blazer you have my sympathy. Autozone or Advance Auto will read the codes for free. Once you have the codes (P0xxx), post back with them and we should be able to help.
Here’s a link with a list of OBDII codes http://www.obd-codes.com/trouble_codes/
Note, a flashing check engine light is serious, ignoring it can lead to serious damage.