I did it with the engine removed so my experience probably doesn't
apply to you.  No.  I did not remove the engine just to do the seal of
course.  With the timing cover removed, I used a 3/4" drive socket of
appropriate size to bang it in slowly, checking alignment after a
couple of blows using a 16 oz hammer.

I presume you are doing it in car.  So you will be staring at the crank
shaft protruding from the timing cover.  I suggest you get a short
piece of 2x6, cut a hole in the center to allow the crank shaft to go
in freely and use it as cushion to hammer the seal in.  Again do it
evenly one or two blows at a time around the edges checking alignment
every few blows.

I did one with the engine in the car.  I seem to recall that I was able
to press the seal in place by hand.  I just pushed it in all the way
until it bottomed out.  This was on a '93 2.3L turbo.