Ranger175c:
I just bought a 300SDL in Texas about a month ago and I'm delighted with it. One of the big attractions for me was that it was rust/corrosion free, something that is almost impossible to find here in the northern climes. If it has spent all its life in Texas or that area it should be rust free, UNLESS it has been hit and badly repaired.
The Texas heat and sun is hard on interiors (especially dash) and all rubber components from the obvious tires to door seals and hoses etc.. I was lucky, my interior is in good shape, as the PO used a windshield shade religiously and the other windows were tinted to reduce the glare. The sunshade came with the car so I'll be able to use it on those two sunny days in August and when the glare from the snow gets too bad
Where is the car? Mine was in Austin and if yours is close by I can highly recommend Ben's Workshop there to get a Pre-Purchase Inspection.
Good luck - the SDL really is a GREAT car.