I softmodded a xbox long time ago and wonder if there is some easy way to update it?
I thought of just ftp another dash and start that from the filemanager and just replace my "default" with the new files, while running the temporary dash? ( hope i dont have to search for my old xbox-usbstick).
Also wondered if the only method to change hdd in a softmodded still is to use my computer(xboxhdm linuxboot) since i dont have any ide connection on my current motherboard
There are methods of installing a larger HD which don't involve XB0XHDM and an IDE equipped PC. Search for chimp or lxhdm or hotswap. (But I always use HB0XHDM, simply because it's what I know best.)
You can also use xboxhdm_2..2a - that uses a linux GUI and can be booted via USB. Not sure whether or not it would work with a IDE-USB USB Caddy but it should work with a standard SATA-IDE converter in your PC.
As for your method of bootin to another dash and then updating, that is the correct way to do it. I'd suggest ftp'ing the new build over to a folder called XBMC2 so you can try it out before making it the default dash (just click on the default.xbe file in filemanager to launch it). If you're happy with it then boot to another dash (Evox, UnleashX, Avalaunch etc.) and then delete XBMC and rename XBMC2 to XBMC.
Don't ever ftp over the old build, always make sure you do a fresh install as there can be compatibility issues, especially with UserData. You might not notice a problem at first but after a few months you can get a whole load of trouble on your hands.