It is NOT on the building so no need to mess with the building at all. The larger container should be pretty obvious, and it has a smaller container stuck in it that you only need to unscrew the cap to access the logbook. This one isn't meant to be that hard, but to have fun with a cool container. There is no need to purchase anything at the establishment in order to search for the cache. If you come in the evening time during the summer, it might be impossible to search for it due to the amount of muggles! So PLEASE use stealth while searching so this one doesn't get muggled. Please no searching at night unless the business is still open.
I hope that everyone has fun with cool cache container!