Well, I wouldn't specifically know. I used to own a 1994 Grand Vitara model. It of course only had a tape deck. Suzuki Grand Vitara's were one of their more slowly technologically developing vehicles. Maybe in 1999 they were outfitted with CD players. I wouldn't be surprised if they didn't though. As I say, Suzuki weren't exactly quick to jump on board the CD player idea and many of their older model cars may not be outfitted with one.
Best plan to go to your local Carsound outlet just in case so you can buy a CDE deck if your 1999 Grand Vitara model doesn't come with a pre-existing CD player set-up.