Make sure everything is backed up! The other question will be if you have the two drives "RAIDED" together or just as two separate drives...? Two separate drives should be simple...
Then, when you hook up the ESATA stuff, see if it shows up as one drive or more than one.
However it shows up, you can start up your LR and in the catalog it should show the photos as "missing" if it can't automatically find them. If they are "missing" photos and folders should have a question mark icon and show the "missing" message.
From there, it's easy to get Lightroom to find them so that you can keep the metadata -- right-click on a "parent" folder and Browse to the related parent folder in your new drive system. Lightroom is "smart" about picking up the folders and images once you point it in the right direction. If your ESATA drives show up as more than one drive, you'd maybe be able to do this in just two operations, one for each drive.