Definitely, call today and ask the vet if they provide the recovery collars. My vet didn't (again, because they really are against them), but there are places you can go to get them..probably a pet store.
Activity: The vet will tell you this, too. She needs to not be super active like running, jumping, horsing around. I'm not sure how shih tzu's are but that was an impossible task at my house for Mandie. I did my best, short of caging her the whole time, but she's a Yorkie..c'mon!
As mentioned before, remember - no baths until the stitches come out.
She should go potty just fine and the same as she has always gone. I would keep an eye on it though just to ensure she is able to poop. Again, constipation happened with Mandie due to the meds and I think it was painful for her to "push". My other pups that were spayed didn't have this issue though (a pom and a small/medium mix girl). It might just be because Yorkies are soooo tiny. I would definitely keep an eye on Julie's poop though and have that mineral oil ready - even feeding her fiber, like green beans could help.