1) No you don't you can soft mod an xbox with linux using the 007/mechassault/splinter cell hack provided its not a v1.6 xbox, look at this site for all the details
This means that you don't have to open it and install a modchip so long as you have a way of transferring xbox saves from pc to xbox (i use action replay) and either one of the games splinter cell, mechassault or 007 agent under fire. You can get those hacked saves from the site above.
2) You can use evox, this can be installed on the xbox using the softhack method. Once you install a full linux distrubution on your xbox, you can ftp to it and transfer files beween the two, you do this by giving the xbox an ip address and gateway address (which you can only do when you install all this).
3) No, you just have to have a crossover cable connected between pc and xbox, or you can connect them through a router if you haven't got a crossover cable and then you can ftp to. If you connect the xbox to the internet after you do the softhack (if you do it) then microsoft will probably ban you and they will also maybe update your dashboard (thats the menu you get when you turn it on with nothing in the drive) which would disable the 007/mechassault/splinter cell hack.
4) Just use a crossover cable or hook them both up to a router.
5) To access the xbox once you've connected it (and modded it or soft hacked it, you can't do it without doing one of those first) just use a ftp program like flashfxp, and type in the ip address of the xbox (that you've given it), user name xbox, password xbox (sometimes is user name root, password xbox), done.
Is that any help?