Hooray for 50BMG!
I'm glad you followed Intell's and my own instructions to the letter, and it's great to hear that the firmware upgrade was a success. It's always nice to see a fix work for someone after you've tried it yourself.
Good job on diagnosing the RAM; I had a feeling the modules were incompatible, since the other possibilities really did not add up.
That's too bad about the WiFi card, but you sound like you know what you are doing, so I'm sure you'll be able to replace it with a new model quickly: the install isn't terribly difficult and it's a cheap part to buy. Could be worse; the logic board might have fried! What a nightmare!
As usual, Intell is correct. The OEM discs you obtained along with the Mac will not work, as it is going to behave (more or less) like an '07 Mini, so get the appropriate discs for it. That is fortunate that you have a friend who can share the discs with you.
You say you will be upgrading the CPU? Good luck, that is a major operation. I'm not terribly worried - I think you have everything under control, and it is certainly a more economical approach than buying an '07 Mini.
Thanks for catching my typos in the firmware bless command - I'm relieved you noticed them before attempting to issue the command in the Terminal and then restarting, only to find that the firmware upgrade was botched.
I'm going to edit my post so it reflects the corrections.
As far as XTools and OS9 are concerned, you should be able to launch them from your upgraded Mac, as long as you are still using Tiger. They will probably also work in 10.5, but I am not completely certain, so I'll let you play around with it.
Oh good grief: you went through all the trouble to upgrade your firmware, and now you want to know how to go back? Ah well, the inquisitive mind is never at rest. Here's what you have to do to downgrade (assuming you get cold firmware feet):
1.) The most obvious solution is to use your firmware restore cd that you created before you performed the firmware update. This should prompt you to restart the Mac, and you will undergo the same process that you did when you upgraded the firmware: the power lights will blink after holding down the power button, an Apple logo with a progress bar, etc. Full details can be found
here.
2.) Download and run the
Mac Mini EFI 1.1 Update but it will only work if you force it to run in single user mode, as the installer will check your firmware version if you run it from the Finder. Because you have 2,1 installed, you will have to force it before the disk is mounted. This is rather tricky, because first you have to navigate to where the update dmg is saved, open it, and then force the package to launch. Even with root access, it might not permit you to downgrade, but it is worth trying if the first method doesn't work.
3.) Finally, the last option, which is more of a last resort if the first two methods don't work, is to navigate back to the location where you installed the new firmware files (/System/Library/CoreServices/Firmware Updates) and either remove them, so the system reverts back to the original firmware, or edit them so they contain the original 1,1 firmware values, and then bless them in the Terminal. I'm not going to explain the entire process, because the first two methods should work. Remember, this last technique is only a last resort!
To answer your final question, no there isn't anything you need to do to use the RAM more effectively; as you've already run a PRAM, nothing else is required - unless you wanted to get really fancy and install a second hard drive and relocate OS X's swap file to it so that it would remove the VRAM bottleneck from the first drive. Of course, this assumes that you are using more resources than your installed RAM can provide, and you are overusing the swap file, which is usually not the case.
Once again, I'm glad everything worked out for you, and if you have any more questions about the downgrade, please direct it to me via PM, so that we don't clutter up the thread anymore. We have demonstrated that a Mini firmware upgrade will work to fix your aluminum keyboard woes; let's keep it on topic, shall we?