I see a lot of services running by default on my Ubuntu system and I am wondering if it safe to remove them from the boot-up process. I am running just as a desktop computer, no laptop. I have a UPS device and I am not sure if the battery monitoring programs are used in conjunction with this UPS device when the power goes out.

Given that I don't use a laptop, do I need to have acpid, hotkey-setup, laptop-mode, ampd, and acpi-support running?

Given that I don't have any cellphone or wireless devices, do I need to have bluez-utils running?

Given that I use a Verizon DSL, do I need to have ppp running?

Given that I have a Brother printer and Brother scanner, do I need to have the HP Printing and Imaging System running?

bluez is bluetooth. Your choice is off, as I understood.
acpid is needed for example, to init 0 by pressing power button on computer.

Well, don't be afraid to try - you just should ensure you can re-enable any service and reboot.

Get a live CD (or some other way of getting into the system).
Backup any configuration files that you want to experiment with, then "just try it". Remove the links in the startup folder for your runlevel, and see what happens. (Good learning exercise if nothing else)

Well, the main thing is to learn how to mount, and how to pass init=/bin/bash to kernel. And to remember that in this mode you need to run sync and 'mount / -o remount,ro'. After that you'll have to work hard to make system unbootable by init script disabling. Maybe you should practice in this before, but daemons you mentioned aren't really critical for booting to console.