Hi fmiller4,
I have two GX680III's and several lenses (50,65,100,115,125,150,180) four of the five viewfinders, the battery packs, long and short extension rails and all of the different bellows. I have the cable release and even a radio release.
Why the big list. a couple of reasons. First, it is a huge and comprehensive "system" that can do just about anything, depending on how you configure it. This can be very daunting at first, but don't let that put you off. It is my favourite camera to use and still makes more than half my income. My point is, you have to start somewhere, and I would advise you to start small and slowly build up a system over time. That way you can wait for bargains. I have bought all of my kit from eBay, and if you aren't in a hurry, what you want will always come along at a price you are happy with. You just have to figure out what things are worth to you. An example is the 50mm lens. This is the widest for the system and equivalent to a 19mm in 35mm terms. I wanted one for years but didn't want to pay $2000 for one, which was the going rate for a long time. There is one on eBay at the moment for $1500ish. But there is also one for $600ish. So it pays to be patient if you can.
As to your question about the angle finders, there are two, and I have both, they are definitely handy, and different. They have different angles, the v1 is a 90deg angle and the v2 is slightly angled up, and I feel is slightly better optically, but both useful if the camera position works (waist level viewfinder is obviously better for low angle shots)
As with anything, you get what you pay for. The III's are newer and "generally" (but not always) in better condition than the older Is and IIs, always look at the photos carefully and preferably buy from sellers with good feedback and who offer returns. Other than that, all I can say is enjoy, I know I do.
Kind regards,
Jason Berge.