If you have just a bit of mechanical aptitude you'll have fun!. You will need to add one step to my tutorial, you'll need to transfer the new crown to the stem so you'll need to remove the old crown. On the GMT Master II I did I just heated the crown a bit with a lighter to break any thread locker that might have been there. I then grabbed the stem right underneath the crown with a pair of needle-nose pliers, and unscrewed the crown. You can then screw on the new crown and test fit it - you may or may not have to modify the stem length. If everything works - time set, date set, winding, screwing down the crown - then remove crown and refit it with a dot of thread locker on the tip of the stem before screwing it snug.
I've bought several crown/tube sets from that seller and so far have been pretty happy with his product. Oh, BTW, I ordered 2 more sets from him last week so I will be doing my Noobmariner when they come in as mine is an old one with the huge crown as well!