Welcome to the party ! Optics give you the reversed image whereas viewfinders reverse it to give you a what you see is what you get image. The waste level finders on a Hassie will in fact give you what the lens is showing, a reversed image. The prism finders, both meter and non-meter will give you a normal L-R image whereas the stovepipe finders don't. After awhile, you just get used to it and it becomes pretty natural.
As far as image size, you can get a stove pipe (vertical) hood that magnifies the image. The newer ones have adjustable diopters built-in to allow for us older types that need longer arms to view things up close. I like those much better than the waist level finders. And the prism finders are sharp as a tack as well. Of course, everything is interchangable.
KEH is a great outfit to do biz with. They stand by everything they sell and I believe their prices are quite fair especially given their level of service and the quality of their rating systems and warranties. I recommend, however that you get an old copy of Ernst Wildi's book "The Hasselblad Manual", even the older 4th Edition will do (cheap at Amazon.com). It covers all the basics in camera operation for all the bodies produced until that time, including the 500CM, along with accessories and how to use them like mags, finders, prism meters, flash, etc.
And if you haven't got it, here's a couple of really useful links for you at
http://www.hasselbladusa.com/ Sign up for the free owner/members access, register your Hassie gear even though it's used and in the owners/support section, you'll find user manuals for all their camera bodies in PDF format.
On this sign-up/log-in page
Dead Link Removed there's a link to their downloads and there you'll find the manuals.
Anything I can do to help you out in terms of usage or particular Hassie issues, feel free to ask. There are others here who are really good with the equipment as well. You can always post in the Medium format section if you're not getting a rapid response in this forum.
One last thing in case you didn't know about this. NEVER EVER try to fit either an uncocked lens and/or an uncocked body together. That can cause really serious damage. If you don't know how to manually cock both of those, let me know and I'll step you through it or send you some more links.
Take it light and stay frosty ! ;>)
Mark