Without an xbox memory card, the modded xbox will be of absolutely no use in modding your virgin xbox.
HD hotswap is your best bet. You have everything there that you need to do it, other than the software. I highly recommend the UDE2 soft-hack (or UXE), since you don't have to expose your xbox MB and solder the jumper points. Just hotswap the xbox HD into your PC to get the necessary software on.
Ldots has an excellent program he made called xboxhdm. Get that, and the UDE package for it, burn your xboxhdm boot disc, and boot your pc with it. Then, hotswap the xbox drive into the pc, and go thru the simple menu-driven install process.
Plenty of tuts out there on this, but few mention the most important thing about hotswapping:
Disconnect your xbox DVD power cable and power up the xbox so that it boots to an error. At this point the drive is unlocked and will REMAIN that way, so you now have all the time you need to do the actual IDE-cable swap.
Otherwise, it's quite a pain to make sure the drive is unlocked when you do the swap.
If this all sounds like too much trouble to you, spend the 20 bucks for a memory card and make it easy on yourself. No need to even open the virgin xbox at all that way!