Yes an OTA update will work and you'll get rid of root. To update and keep root try Odin mobile, it used to work if you flashed new firmware by downloading the file and using mobile Odin to flash the downloaded new firmware file. I haven't used it since my SGSIII days so I don't know if keeping root is that easy anymore.
Right what to do now your rooted, well anything, first thing to do is install a custom recovery so you can flash .Zip files that can be mods, ROMs or kernels. I recommend Philz touch, it is user friendly and has many options, some you might not need, but are handy to have. Once you have installed a custom recovery "do a Nandroid" before doing anything else. This is basically a snapshot of your phone as it is working, as long as you can get to recovery a Nandroid is your get our of jail card. It can be used to instantly get back a working phone. Make a habit of "doing a Nandroid" before you flash any mod, Kernel or new ROM and if it goes wrong you'll be OK. Nandroid files are huge (often a Gig or more) so either delete old ones or better still label them in a folder and stick them on a PC or hard drive. Just keep your original one and perhaps the latest one on your device. Donot alter their names though (usually a date format) as doing so will cause them to fail an. Md5 checksum on use.
First thing on my list after rooting, installing a custom recovery and a Nandroid - change the status bar battery icon, the stock one is plain ugly.