If you are going to set the timing
If you are going to set the timing, I'd just wait till then to do the front seal. Taking the fan, fan pulley mount and fan shroud off and out of the way makes loosening the nut and setting the timing just that much easier.
Also while the cover is off you can loctite and tighten all the bolts under the front cover that can come loose and do the same type of damage that the infamous dowel pin can.
If you have the front cover off, then it is very easy to clean the pump shaft and the gear's tapered mating surfaces so the timing wont slip. Get a new wave washer for the pump nut too, often the old one is cracked or in two pieces. They're just a few bucks from Piers.
Just setting the timing only requires unscrewing the oil filler to access the pump gear nut, and put a puller on the gear to pull it off the tapered shaft. Cleaning the taper requires using a can of brake cleaner with the plastic spray tube and trying your best to wash all the oil out of the gap that you can't see. Having the gear in your hand makes this much easier.
Hope this helps Greg L.