I assume (since you can boot up to the Xbox dash) that you managed to flash the bios all ok - well done

Always try and leave bank 2 unflashed - that way you can select bank 2 and boot up to the Cromwell Flash Utility to "re-flash" should you ever need to
As for dashboards, EvoX and Avalaunch (my preference) tend to be the two most popular alternatives. Have a think about which you'd prefer (plenty of info at xbos-scene), and obtain a copy.
How to install? Briefly:-
1. Configure the network settings in the .xml file so that they match those specified
here (*important* - failure to do this correctly will prevent you from being able to access your xbox via FTP - make sure you get it right

)
2. Next step is to create an iso disc (which your Xbox can hopefully boot - you may need to try a few different media types if you have trouble). See
here for details and essential info. Once you're done, pop it into your xbox and (hopefully!) you should boot to your chosen dash.
3. Next step is to use a programme like FlashFXP or CuteFTP to access your xbox - see the network settings thread above for details on how to do this. Once you're in, copy your dash (
all relevant files - this will vary depending on what dash you've chosen) across to the C drive of the xbox.
4. Shutdown, and reboot your xbox - voila!

(Once again, hopefully

).
The alternative to all the above, is to obtain a copy of Slayers auto installer which will enable you to install a dash directly from CD (i.e. no need to use FTP) - certainly easier for a beginner, but FTP is an essential tool/skill if you want to do much more with your xbox. The choice is yours but I would highly recommend at least trying the FTP option
A
very brief explanation (my apologies), so if there's anything you're unsure of don't hesitate to report back. Do try and make sure that you're well up to speed on the procedure before you make a start though - there's masses of info around that will help you understand what it is you're doing in more detail, and make matters proceed more smoothly!
Good luck,
Kelvin.