So very, very sorry to hear of Gracee's passing. When you've had them that long, it seems like they've been there all your life, and it's a terrible shock when they're not anymore. My Neechee died in 2010 at 17-1/2. I'd had him so long that I couldn't imagine life without him.
I know that he and my Border Collies Max and Maggie will be there to greet me at Rainbow Bridge! Have faith, dear ones, and Gracee's memory would be honored if the memory of her led you to get another Sheltie.
It is so hard losing a dog - they become such a part of us, in heart and soul. Their short little lives are just no long enough, yet they don't care and still live life to the fullest no matter what.
I pray for comfort for your grieving heart, and peace for your soul.