Been there done that, and they are doing exactly what should be done. Despite the fact that there doesn't seem to be nodal involvement, it's better to have the neck dissection. This cancer can seed to the nodes and this will not show on a scan. So they remove the cancer, leave the nodes and then a month or two later your nodes flair up! then you are facing another surgery and / or possible rads and chemo.

And despite the early stage this is VERY possible. SO better safe than sorry, and if they do remove the tongue cancer and the nodes and you get an all clear in the nodes then chances are you may have dodged the rads and chemo bullet. Best of luck my dear... and kick it in the butt.

PS the surgery - is okay... and doable. It's a big surgery (I had 1/3- 1/2 of my tongue removed) about 10-14 hours and includes a graft of your tongue, but pain wise it's not too bad because they cut the nerves in your neck (you'll need phsyio on your shoulder after) so you are numb your mouth will hurt but it's manageable. Within three to six weeks you'll be bopping along okay.
(the large time frame depends on our overall health and healing speed)

Coming out of surgery you will have dressings wherever they took the graft from, stitches in your tongue, a nasal tube for feedings, a catheter, an IV, possibly a trache (you will need a pen and paper of ipad to communicate with for a few days) and a few drains. You will look like you've been hit by a baseball bat... but you will be okay!