Sorry about Wally mate, no doubt it's pretty horrible right now. Don't beat your self up about not crying or what ever just now, I was the same when my Grandma died a couple of years back. We all knew it was coming, she had cancer for a while, she finally died a week or so after new years (holding on so everyone would have a happy holiday was so like her) but when I found out I didn't cry a single tear. Which I felt pretty bad about.
At the funeral how ever, cried my fucking eyes out. So yes, in summation, don't be too hard on your self mate. There is no strict rules regarding mourning, just do what you need to do to remember the memory of Wally and don't force anything.
RIP Wally!
Jam it back in, in the dark.