Simple:
Go to Goodsam.com
Click on the link in the upper right corner of the page "Sign in".
On the sign-in page, enter your email and password (same you use for RV.net most likely, considering you have the Good Sam logo on your profile (left of your post). Click "Sign in".
When the next page comes up, click on the "Account" link (upper right corner of the page).
Click on "Account" from the drop down box.
You'll have your information right there. Your Member ID and your expiration date.
You can also print a temporary membership card.
Good luck!