"If I buy a pandora battery and magic mem stick i can plug in the battery and mem stick and run the update?"
Yes. Although if you make the MMS correctly it should update straight to the CFW. I don't know if you're going to buy the MMS or just use your regular memory stick to make one, but I'm going to do a preemptive answer and link you to two MMS creators that'll let you do everything on the PC without the need for a CFW PSP. http://tinyurl.com/37kgf6 and www.catb50dev.co.nr
"Can I use the same battery for normal use or do i have to buy a spare?"
No, not unless you buy this one: http://tinyurl.com/2oakrk
You can convert normal Pandora batteries back, but it depends on the method you used to create them and if you backed up the nand-dump.bin by pressing Square at the Pandora menu when creating it. With the one I linked you to, you shouldn't have to worry about it. I'm just saying this for the sake of being politically correct.
"Pandora Battery: it is pretty much a homebrew enabled psp but its a battery right."
Not exactly. Pandora is the battery used to boot your PSP into service mode. The homebrew enabled PSP (aka Custom Firmware) resides on your PSP's internal flash.
You can however, use Pandora and Time Machine (an app) to boot a CFW or any other firmware from the memory stick. Time Machine might be a little advanced for beginners, so just take baby steps if you plan on doing this sometime in the distant future (there's no real benefit). I've got some links to other guides handy... was thinking of posting it as a tip.
