To cook simply go by the rule of 15mins per lb. To avoid overcooking check the goose 30 mins before end and every 15mins thereafter.
A cooking thermometer is a really good help here!
Insert a skewer into the thickest part of the goose.
If the juices run clear, the goose is fully cooked.
If juices run pink, continue cooking for a few minutes and re-test.
Check that product is thoroughly cooked before serving.
Allow product to stand for 30 minutes before serving
Use a deep roasting dish as the juices from this bird are more than you might expect from a Turkey.