Different autobox in the diesel model to my petrol engine. Both are 5 speed with paddle shift and sport mode. No problems with mine, its smooth, and you can always use the paddles if you want to change gear, so best of both worlds. Mine 2008 with 75k miles, just due the fluid change, £75 at a Honda dealer.
Just check it does clank a lot when you put it into reverse or drive when cold, check the changes are smooth, the paddles respond etc. Also whip out the auto box dipstick and check the fluid is clean cherry colour and topped up.
Believe the auto hurts the economy on the diesel quite a lot unless you do a lot of motorway work, around town its pretty low.