Hi, buffalobluff. Premiere Elements has its own forum, and it's better to ask PRE questions there, since not many of us in the PSE forum use PRE. I'll move this for you.
What are you heading for with this video of your autobiography...export to file saved to the computer hard drive, burn to DVD-VIDEO standard or widescreen on DVD disc, or burn to Blu-ray disc format on Blu-ray disc. I do not know the quality of what you are getting from the Logitech C920, but I believe it offers 1080p footage. So without further information I am moving in that direction rather than Hi8 tape based choice. But I have my doubts about the Logitech being able to handle the green screen. I continuously see online recommendation for more expensive cameras designed for that type of work. Have you done a mini test run with what you have? In one article I saw the recommendation to rent a camera specific for the task.
If you are going to be doing green screen videography, I would not be using Videomerge. I would suggest the Green Screen Key Effect for a green screen prep for starters.
But the preparation for the green screen preparation is very important. Have you looked into the lighting et al that goes into that?
Just some thoughts. Have not been there and done this first hand except for the Premiere Elements workflow side of things.
I agree about Keying with another Effect, than VideoMerge.
Also, effective greenscreen work starts with the greenscreen background, and then the lighting of that. The better the lighting and the background, the less work one will encounter in post-production.
This article links to a good greenscreen resource center: http://forums.adobe.com/message/2561427#2561427 and there are plenty of tutorials on lighting the background, and the subject, for effective and efficient greenscreen video. I would study those in detail.
As for the actual recording, and camera that produces material that can be Imported, or Captured, should work OK. The quality, however, will depend on a lot of factors, such as the lens, and the format that they record in.
It is good that you are planning this Project out, before just shooting. That will save you grief and extra work, later on. Too many folk just grab a sheet, paint it with greenscreen paint, ignore the lighting, and shoot whatever. They usually create much more work for themselves in post-production, but if one plans the shoot beforehand, and does the setup correctly, some amazing work can be done with greenscreen - just look at almost any Hollywood action move.
Good luck, and others might be able to offer you more direct advice on which camera to shoot with.
From the what I have read collection, these online articles seem to have tried to target the question of which camera best for green screen work
The above links are not intended to promote one particular camera but rather to demonstrate the type of factors that enter into the discussion of what camera to use for green screen.
To give yourself a baseline, do some mini test runs with what you have and see how that all works or does not work for you. Then shop or rent camera wise.