Yes, you can. The seals are mounted in the little points and advance unit housings, not the head itself. Remove the little housings (3 Phillips screws) and you can do the seal replacement. You will need new gaskets for the housings. There is an o-ring on them too but as long as you don't damage it, you can probably re-use that. I mention this because I don't think Mike's sells just the o-ring separate, only in full gasket or o-ring kits.
You'll probably find the ends of the cam that stick out past the seals all dirty and rusty. Many times, this is what starts the seals leaking in the 1st place. That dirt and rust works it way into the seals, causing them to leak and sometimes ruining them. While the housings are off, buff the ends of the cam clean and shiny with a Scotchbrite pad.