Best way to adjust to new dog/puppy?

Depends on the dogs.  One of our four, Tasha, won't let one of the others, Pepper, play with toys.  So we have to shut her in a room when we want to play with Pepper so she doesn't bully Pepper.

I would NEVER crate two dogs in one crate without knowing they will be fine and not for a very long time either.  Two of our 4 can go in one crate for short periods of time and they actually do better together in a crate, than each of them seperately.  You just don't want to risk fights.  The two that crate together only do so at trials where they are not crated together for long periods at a time.  And they grew up together as well.  I didn't start doing this until necessity made it so though.

I would assume they could use the same litter box but you'd have to experiment and be prepared to get another one if not.

I guess it depends on the dog.  Some dogs can get aggressive over toys, and it can trigger fighting, or problems at the least.  I would guage your dogs.  To start out, at least, I would get the new pup its own toys.
 
I also agree with Tashakota about crating.  I would not crate them together until you know it is ok.

I also agree on the crating issue. We would definatly not just put them in a crate together and leave. It would take some work to know that it wouldn't be an issue. My husband was just thinking that they would might like to be together.. assuming they got along.
Also I think with the toys that it's fun to get new stuff for the new dog anyway. But I didn't know if they would not want to share their toys.