Ok, I am fairly new here and I had the same exact questions you have. But the only difference is that I did research and ONLY asked questions that I could not understand. First you need to go read the tutorials on XS, they will explain most of your questions. Second, I understand your situation and will provide you with the order in which to mod your Xbox.
1. Modchip with bios that allows hhd swapping.
2. since you have a Matrix modchip it will be very easy to install it yourself. Go to XS or got
to www.easybuy200.com and click on the matrix modchip and there is a tutorial there.
3. find Evox dashboard and burn it to CD-RW or DVD-R as an xISO.
4. verify modchip is correctly installed and load CD-RW/DVD-R, if you installed the modchip
correctly and burned the xISO you should instantly know if you done it correctly when
the Xbox dash appears and below the big green "X" it says "Matrix Inside".
5. FTP everything in the original Xbox hhd, make a backup copy of C/D drive. FTP back
everything back into the new hhd.
6. Now you have a perfectly modded Xbox and you just need to load the applications you
want.
Of course this is just a general step-by-step process and every step can be found in the tutorial section of XS. Good luck and enjoy, trust me when I say you will feel a "Xstatic" when you accomplish this yourself.