My experience with this problem has been a bent inside door handle that eventually breaks completely off, but before doing so it gets harder and harder to release the latch.
Another possibility is kiddy lock but this would be unusual on a driver door unless the handles and locks had been swapped over at some stage. It is usually fitted in back doors so children can't open the door in a moving car.
Here is a great link to remove the interior door handle. It is not a big job.
http://www.bodyshopzone.com/archives/trim/door_panels/Chevy/CK1500_1998/dp_remove_chevy.html
Also, I bought the replacement handle assembly from the local Advance Auto Parts store. It was a perfect match for the gray interior of my 1999 Suburban, and cost only $16.
You will have to drill out a rivet, but it can be replaced with a simple machine screw when re-installing the new handle assembly. The assembly fits into the door very tightly with some teeth that you will see on the back of the unit, which will also help you see how the old one will need to slide in order to be removed one the rivet is drilled out. All in all, this whole repair should take about an hour. And it is great not to have to roll down the window to get out any more!
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Get under the driver side of the suburban by the driver door and their should be a linkage that you can loosen
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