Puppy!

 I have four dogs, two of which are herders, and I split my time well among them, so I'm sure if you make the effort you can too.  Collies are easily trained, but they need a LOT of early socialization (from age 8 weeks on) with both people and other dogs of all ages, sizes and genders.  So, that will be the time when you will be spending a lot of time introducing your pup to the things you want her to tolerate when she's older.  Herders can be suspicious of strangers, so the more people and dogs you expose her to the better (just keep things safe).  Find a good positive trainer in your area - they often run puppy play groups, too, and will be able to help you find compatible pups.

I already own a Collie- so I am well aware of the socialization. Along with the breed itself. :) I think Zeke will be happy to be a big brother though. So things should go smoothly. I am pretty excited. I have had Zeke since he was about 6 weeks old and he is 6 months now. He has been awesome. Not to mention one of the most intelligent, easy learning dogs I have known! So I am not at all worried about the breed or training.