OP, I'm so sorry to read your post.
Shepherd, I hate to think what you're going through right now, the same happened to my gorgeous Jimmy many years ago and I still shed a tear to think about it now. I can't say anything that will make it any better, but please be assured that I'm thinking of you.
OP, my mum's collie x (my childhood best pal) sadly passed away with cancer a few years ago. He had an amazing life, filled with laughter, long walks, and cuddles. He had also seen my mum through two marital splits, two kids leaving home, deaths of several other (human) family members, and remained her constant loyal buddy throughout.
A few weeks after he passed, my mum saw a notice on a newsletter from the rescue centre from where she'd re-homed him 12 years earlier, advertising a new home wanted for a (different breed, different age, different temperament) boy with the same name. She saw it as an omen (if you believe in that sort of thing). It was Grand National day and there was also a horse running with the same name as Dog1 and Dog2.
Fate was watching her, we went to visit the centre that day, and Dog2 came home with us (both of us were in floods of tears all the time we were there). You couldn't imagine a more different dog to Dog1, but Dog2 has certainly made his mark on her home and brought her much happiness. He wasn't a replacement for Dog1, but instead he filled a different place in her heart and is just as loving and loyal (although more daft and totally different personality-wise) as Dog1.
Like a PP mentioned, Dog1's ashes still live on a shelf in the living room, and it's still the done thing for all family members to say hello to Dog1 and pat the box as we walk in!
We also sponsored a kennel at the rescue centre in memory of Dog1 - it costs a couple of pounds a month, and we were able to choose the wording for a plaque in his memory on the wall next to the kennel. This really helped my mum make the transition, as she felt that Dog1s memory was able to live on by way of a good cause.
HTH and thinking of you x