Many excuses for my not very useful first post, but here it comes:
I just was succesful at installing and getting to run usbmode and xptools!
After lurking the forum for half a year and trying to get my a780 to bend to my wishes, now I can use eakrins ezxmpkg
For all those still strugling: do not dispair. I did not have any feedback during install, because I didn't figure out how to install ezxdialog yet. My phone is a European model, so it took a bit of trying out before everything ran like it does.
The steps followed, as far as I remember (I got linloader -presumably- correctly installed almost a year ago, using troodons' howto, http://www.troodon.org/a780/files/ba...s/loader.zip):- tying to get usblan, no success (
Get a shell - OpenEZX)
- reading more about needing linloader to get (m)pkg's installed; at first didn't get the clue that even though I got the option of "long-clicking and install" was available, it probably does not have effect.
- finally settling with ezxpackgage, it's advertized for noobs here anyway
http://www.motorolafans.com/forums/a...ed-phones.html
- since I was not sure about linloader working correctly (got the test text, but no further successes), I was afraid ezxmpkg would not install so I googled for mpkg and ezxmpkg. Gave links to motorolafans and quite some Thai and Russian/Cyrillic websites. I think I used
http://www.motorolafans.com/forums/a...80-0.3_645.zip from
http://www.motorolafans.com/forums/d...680i-a780.html
- I had no idea whether it was succesful yet. Restarted the phone, renamed some of my .mpkgs to pkg to be able to choose long-click + open with instead of long-click + install.
- waited for a minute or so, before power cycling the phone again
- with my hearth pounding, I opened the applications menu, and didn't see anything new (slipped my mind that it defaults to the office programs, can't figure out why)
- changed scope to all programs, and there were they! Ezxmp..., XPTools, USBMo..
After that I rushed back to the forums, and now I am going back to see what else I might install 
Thanks all noobs for asking the questions I had, and thanks all experts for answering them so nicely. There's such an overwhelming lot of info on this site!