I am looking to purchase my first S class and couldn't be more excited. I have found one that seems to be at a good price and I wanted to get others opinions on it

2008 Mercedes S550 4Matic
56K miles
P2 Package
Dynamic Seats
2 owners

The car looks clean and carfax/autocheck dont show anything negative (no accidents, problems, etc).

Two questions:
1. Is $28k a good price for this car? This is what I have negotiated down to. KBB shows it private party sale good condition at $34,100

2. I am concerned about the transmission issues people have been saying they have had with Mercedes around this timeframe. I used the VIN Decoder and found that it has the following info:

Front axle: BE701281104105
Gearbox: 722961 01 638943
Class: 1
Infotable on engine: A01000273 47

I have heard that people have had problems with the 722.9 transmission. Is this something I should be worried about?

Thanks!