ibook g3 logic board

Hi, I need to replace the logic board in my ibook g3 800mhz. If i remove the old one and install the new one, will it boot up and work or will i have to reinstall the os? I don't have any discs since i bought this used, will i have to pay like $100 for the os?

If the OS is on the hard drive already then it should boot up just fine. If not then yes you will have to buy a license for OS X. However since it is a G3, you could get away with an older release. There are plenty of copies of Tiger on ebay, just make sure you get the black retail disk and not the grey system restore disk.

Thank you
The os is on the hard drive. What if the new board is a 700mhz or 900mhz will everything work if i just plug it in?

What if the new board is a 500,600,700 or 900mhz will everything work if i just plug it in?

Well, I don't know for sure, someone else will have to answer that as I don't have much experience with G3 iBooks. There might be differences in the board itself which make it incompatible with your system. As far as the installation on your hard drive itself, it will work with whatever you put in there.