Installed new valve stem seals

I just got some 3/8 Crower viton valve seals at the swap meet and the guy said that I needed an installer to get them on. I saw some 5/16 hemi seals and those came with a little plastic tool that fit over the seal and pushed them on. He also said the guides had to me machined for the seals too, of course this was told to me AFTER I bought them, but they were only 5 bucks. Can I just push them on? I believe the old X heads are already machined for these style seals, a very small width guide as compared to my 86 360 heads that had thick guides, umbrella seals and some huge black plastic cap looking seals that were petrified.