I just had my MB Tex seats recovered in GAHH vinyl and can provide a couple of observations. The vinyl you buy today is nothing like the original vinyl. I agonized over my interior for a long time but my original MB Tex seat covers were really unserviceable. The grain of my original MB Tex is deeply carved and quite striking. In comparison, the new vinyl has very little relief.
I paid a shop $3,500 to cover the 2 door cards, the seats, the top dash pad and the pad on the soft top hatch which was more than the material from GAHH cost. So, if you think you want leather, keep in mind that, unless you plan to do the work yourself, the cost to install is a factor - it shouldn't cost more to install leather than vinyl. Knowing what I know now, with all the guidance available here, I would have taken a stab at doing it myself - but at least its done.
So, if your original MB-Tex will work with a good cleaning I would suggest keeping it. If you have to replace and are considering leather, bear in mind that the install cost is probably the same for leather as for vinyl and that the replacement vinyl won't look much like the original.