Hey Boni,
My advice would be to get a dual deck - DVD & VCR combo. It will be able to do the VHS & VHS-C formats. I have one but haven't done any conversions. Somehow I think they do it at a higher speed than just playing and copying.
As far as the 8mm - I have no clue how to go about doing that. I have a few tapes that I have lost due to the camera dying. As a matter of fact our newest camera - a VHS-C just died and whe have no clue what we are going to get - whether a hard drive or flash memory type. I do have to say this age of digital is a PITA to me ... it seems 10x harder to transfer the stuff we take to a usable format - heck we don't even look at the picts we take!
Back to the DVDs though, I have heard that the re-writeable (RW) are prone to losing their data - I would stick to the write once types and buy high quality ones at that. Sony, HP, TDK to name a few.