Hey Andy

A couple of things.... when you test drive, come almost to a stop and see if the change down is smooth.... then do the same again and begin to accelerate gently before you almost stop ( like being in traffic)... if it is smooth.. happy days... if not there are plenty of threads here about slamming trans...

These things have trans that work and trans that don't and you will soon see by how long it takes to get into reverse, what kick down is like etc... I've got a 4.4 that kicks like a mule and a 3.0D that is as smooth as silk...

Also, check around front of engine and valley for oil leaks...

It looks nice.... good luck

Cheers