I second that, just unzip, install, and go to town. Even worked on my "dummy" client that I made forever ago so it should also work for an already operating system without worries.
As for sizing I personally not seeing any "colliding" of menu items even at the top.
Get the job done and all it needs to do. Now my Blesta install more match the leading billing platform now that my clients will be able to query the emails that the system/I sent them.