I recently purchased a 97 Blazer LT. I din't Get a remote or a manual. How do I find out if the vehicle has a keyless remote system, and how do I program the overhead consul & garage door remote.

Look under the plastic kickpanel (under steering wheel) for anything mounted in there.

To program the overhead console:
Push both of the buttons at the same time for a few seconds...then you'll see them reset. You can do this everytime you fill up your gas tank along with holding down the trip odometer button by your gauges (I do both everytime I fill up). To set the compass, drive in a tight circle (preferrably a parking lot) about 3 times. It should then reset itself and you'll be able to get a heading. To program the garage door opener you'll need the actual garage opener itself. Hold whatever homelink button you want to program (I did the middle one) untill it starts to flash, then open the garage door with the actual opener. The homelink should read the code sent out by the opener and then program itself so your homelink will now work. Hope I helped you out.

I noticed a while ago that I have a flat plug that looks similar to a trailer hitch hook up under my steering wheel. Any ideas what this is?

if im not mistakin thats your comp hook up plug a tuner in it or for diagnotics