I've kind of got the routine and knowledge for how to do this now. I've managed to acquire, softmod and upgrade 2x original xbox consoles and I'm in the process of getting some cool homebrew software on them. I'm able to softmod the consoles, upgrade the hard drives (up to 2TB), install loads of cool homebrew apps and custom dashboards etc. There are a few limitations to this right now, such as requiring the original hard drive still in working order, but I'm working on getting ahold of a large shipment of quality hardmod chips and learning how to bypass this limitation. I'm also working on some more physical upgrades such as new cases, LED's, wireless controllers etc etc.
If you want me to help you out with some knowledge, feel free to ask. If you want me to help you pick up some of the correct parts to do this yourself also I'll help with that.
I'm also going to keep a lil blog of what I'm doing here, just because I think it'll be interesting for everyone.