<VV> oil leak at rear of engine - need your help!

[rbkj84 at comcast.net]

I have a 65 Corsa 140.  (Many on the list will be interested to hear that my 17 year old son has pretty much adopted it as his daily driver!)  I am tracking down an oil leak that developed about 2 months ago.  Its near the rear of the engine.  It seemed like it might be near the distributor so I changed the distributor to casting gasket. No luck.  Then I got more agressive and replaced the gasket under the alternator/oil filter/oil filler casting and the viton seal on the fuel pump for good measure.  But no!  So........ my next thought is that it is the seal that goes into the rear engine casting just behind the harmonic dampener.  The front of that casting looks pretty oily.  The oil is being slung up to the underside of the engine lid.
Questions:  How tough is it to remove the harmonic dampener?  How do I keep the crank from turning when I try to unscrew it or will just leaving the car in gear with the wheels on the ground hold it all (4 speed manual).  Is the bolt that holds on the dampener to the crank threaded in regular right hand threads or is it one of the few that goes the 'wrong' way.  Should I replace it with a grade 8 bolt for good measure? Can the alternator/oil filter casting be left on? Do I need to drop the rear of the engine down or can I do it with that small puller that Lon sells and indicates is very good for this job?  Can I get to the seal behind the dampener when the dampener is off with the engine still in place?  In the tech guide there is an article saying that the seal can't be worked on without the engine lowered but in another article in the same source it appears that the seal can be R and R -ed with the engine in the regular position.  How tough is it to put that seal in and make sure
 that it is in place?  
I have (obviously) never done this procedure before and would appreciate all the knowledge and tricks of the trade before I venture further into the search for a cure!
Many thanks to all for sharing your expertise.
Regards
Ron
65 Corsa 140 Coupe 
64 Spyder Coupe (Power Tour 2006 veteran!)
91 Buick Reatta Coupe

PS - just saw three Tuckers held in private collection.  The largest concentration of Tuckers in one place anywhere in the world !!   Too Cool!!