[jontz]

OK, first things first: The 4100 doesn't do JBOD, so you might have some problems converting your array to JBOD unless the 705 is different and does support the function. If it doesn't (which I suspect is the case) and you want larger drives, all you need to do is backup your data on the current array, pull all the drives, install new, bigger drives (if you want to install 120 GB drives, if not, re-init them as blue said leaving drive one in place), set up your new array, and then copy all the data back.

I would upgrade the OS after you have backed up all your data and before you install your new drives (or re-init your old ones), if you are still planning on upgrading the OS. Just in case something goes horribly, horribly wrong.