The 3M product has a glossy clear coat - some other manufacturers do not - and they (3M) say that it is fine to wax the film.
Also one of the biggest kit sellers over there in the 'States now recommends that wax should be applied straight after fitting to minimise any staining.
Still, you need to be very careful about what sort of wax you use, and try it on a piece first to make sure that it doesn't stain.
Also be careful with chemicals such as metal polish, for doing chromework, etc. One of our customers used something called 'purple polish' to clean an alloy bull bar, was not careful and left a horrible purple stain on the film. So either mask the film prior to using such chemicals or at least try it on a scrap of film. Ask your installer to bring some scrap pieces so that you can try your favourite car care products on the film before it goes on.