Fluids - What To Do?

So, my 330 has a small leak I am not sure what though. The bottom of the engine has some fluid on it, the box has a little and the steering rack has a fair bit on it. Its definately not water and its not pouring out, but my engine oil level doesnt seem to have reduced and while the steering fluid is nearing the bottom of the dipstick, its certainly not bone dry.

This leaves the box. I have checked the sum plug and its dry so it could be that it is fluid on the engine being pushed back over the box when the car is in motion. I cannot check the box fluid level myself but wonder if its worth having new oil put in this anyway - which opens up a can of worms in itself. Car has done 70k miles and I understand the gears somehow adjust themselve when the box oil gets older and putting new oil in there could potentially lead to a severe failure. so if the box is now half empty, I would have no choice but to fill it with fresh stuff. Not a great design in my opinion but anyway...

Has anyone had experience of refreshing their auto box oil?

Also, is there a specific ATF to use in the power steering system or just any old ATF from the local garage?

I am thinking of taking it to Cooks Ferry as they are local to me and i've heard good things, however recently someone said to me they didn't rate them. Any comments in this regard?

Thanks in advance for any help.

jamie