Repeat, often, to your wife:
"I love you, and thank you so much for everything you do for me!"
Do this again.
Just bear in mind the old joke - "looking for woman with fishing boat - send picture of boat" /forums/images/graemlins/wink.gif. Sure, she is probably looking to get some work out of you (or is enjoying such a nice tractor herself, which is also a Good Thing), but my goodness...that is a really nice tractor.
Congratulations on getting a great machine, but even better is the woman that made it happen. You'll be very pleased, I think. This is, BTW, much more fun than any video game you'll ever play (unless they come up with "Tractor, Virtual Reality" /forums/images/graemlins/grin.gif).