You need to install an alternate dashboard, otherwise it will always boot to the MS dash. No, you don't need to update your bios. Everything should be fine, and you can tell because of the EvoX or Xecuter Logo that is being displayed before the MS dashboard loads.
The easiest method is to download an auto-installer disk like Slayers. I think the latest edition is Slayers V2.7, but I haven't had to find something new in a couple years. I can't tell you where to find it, but Xbins might have it. You can find an Xbins tutorial
hereIf you can't find a Slayers disk, or one of the hundreds of other auto-installer disks, then you'll have to manually make your own EvoX dashboard disk. Either search for how to do this or I'd bet there is more than a few tutorials on the main Xbox-scene website that detail how to do that.