I have a 1984 Steinway B, and it is a magnificent instrument! Full, rich, resonant sound. For Steinways, 30yrs is not that old, especially if it's been cared for.
Like any fine instrument it will need regular care to maintain its superior performance, but I would not say it would be extraordinary. If you are going to have an instrument of this caliber, it's worth proper care. And I would recommend you have a Steinway-trained technician working on it. If possible, I'd also have a trained tech look at/examine it just to be sure.
The keys are plastic, not ivory - will be no yellowing/cracking. Keys have not been ivory for a long time.
Based on the pics, it appears to be in excellent condition, but there's only really one way to tell. You have to go and play it.
When I got mine, I knew it was a good piano, but I didn't care for the sound - it was muffled and "tubby" - dull. I found a great tech who worked with me on the voicing it each time it was tuned, and we achieved an extraordinary sound. This would happen with a new piano straight from the factory - you would have it voiced and adjusted till it suited you. These are items of personal preference - do you like a brighter, crisper sound? Something more subdued? It's all a personal thing. BTW, "voicing" is achieved by work on the hammers - loosening the felt, packing it tighter, shaping, etc.
Purely based on the pics which show a good condition, I would say the price is very reasonable. These are $80-90,000 new. I can't imagine you would be happier with the Kawai when you have an opportunity to own a Steinway.
This model is considered the 7' (actually 6'10") and was made for recording studios and smaller concert halls and auditoriums. With your windows open, you will be heard for some distance. The instrument and the sound are big. Keep this in mind. It will be large in your space. I happen to love a big sound. Consider your surroundings and neighbors.
I highly recommend you investigate this instrument. I couldn't be happier with mine. They are beautiful.
Best of luck.