If the trans is out this is the hard part.  All you have to do is take the
bellhousing off (really simple) and then screw the mainshaft back on.  Slide
the shaft collar back down on the splines and put the new snap ring on.  I
would check to make sure that you get all of the broken pieces of the old snap
ring out though.  When you put the bellhousing back on you need to seal it.  I
used some RTV (a very thin film of it).  There is a paper seal there.  I
didn't know where to get one of these so that is why I used RTV.  If you have
some mechanical ability (and a pair of snap ring pliers) this is not a bad
job, take you about twenty minutes.  If you don't have mechanical ability then
pay the money and let someone else do it right so you don't have to worry
about it.
Ken Wilford
Van-Again
John 3:16