how old is that information or in other words: do i still require bootloader V7-pre4?
Yes, you still need 7pre4. There's been a little talk lately of updating the bootloader to fix the boot-from-CF bug that still causes that pesky ata-80 error when you try to boot directly from the CF card.
means first of all i have to flash bootloader v6 and afterwards within rockbox using plugin iriver_flash to update to V7-pre4?
That pretty much sums it up. I think the instructions are mostly aimed at people who already have Rockbox installed on their hard drive. I'm not sure if there's a way, at the moment, to do the CF mod if you don't already have Rockbox installed on a hard drive.
I'll also point out that iriver_flash is actually a much easier and safer method for flashing the bootloader than the original iriver method, even if you stick with the hard drive.
TODO list for the upcoming bootloader revision
H100: Support USB Diskmode for CFModded players
i cant access the player via usb anymore??? if yes, how else?
I'm not sure exactly what the original intention of that was. The current state of bootloader 7pre4, as I understand it, is that it does everything correctly with CF except
boot directly from the CF. With CF you have to flash Rockbox to RAM or ROM for the bootloader to work correctly.
Accessing the player via USB in the bootloader does
work, but it's set up to automatically boot from the disk when exiting that mode, just in case you uploaded a new Rockbox revision. Since it can't successfully boot from CF, though, this causes ATA error -80 and you have to reboot with the reset button. As a result it's much less of a headache to use the USB mode inside Rockbox (after booting), not the bootloader USB mode.
If I'm interpreting your concerns correctly, I would advise you that there is very little not to like about the CF mod. Chief among those is the bootloader not being able to boot directly from the card. That's not really a problem, though, if you just make sure you turn on the player before connecting it to a computer.
The only other problem is that you can't boot the original firmware with a CFmodded player. That's only a problem if you care about the original firmware, though, which I stopped doing years ago. The only thing it has over Rockbox is the ability to play files with DRM.