I used that kit before. Make sure you measure your squirrel before you buy it. That kit comes with a fox squirrel form that is way too big for the average gray squirrel. I bought things individualy from
www.vandykestaxidermy.com. Measure your squirrel and order an apropriate form. Get some black glass eyes. You can use Borax as a dry preservative and some common size wire for your tail. There is a really good book out there by David Ellzey. It is very helpful and what I used for my first squirrel. Here is the link
http://www.vandykestaxidermy.com/product/01007544/. The running up or down is a very good form to mount your first squirrel. It is a forgiving form. For instance my first squirrel was in a running down position and it turned out the form was too big. I stretched the skin as far around as I could and when I stapled it to the belly and put it on a log you could not tell that it did not completely cover the squirrel. Hope this information helps :-)