Help

I'm planning on doing some video this evening for a friend. He is a local musician and he is going to be performing in a Low-light bar setting. I'm terrified by this. I'm not a videographer lol. I'm going to be using my D750 with 70-200mm2/8F lens with a Tri-pod.
Am I going to be able to do this??? I'm just trying to help a friend out promote his music. I plan on putting the camera in Aperture-Priority and let the camera select the shutter speed(Which I know going to be very slow). Are my videos going to be blurry?? He's going to strumming a guitar and singing. Any help/advice Please????

Can you get in before the show and have him sit or stand in the spot with the lighting on to try some settings?
Try different ISO settings, 1600 is the max I go on my D750 for night still shots more than that might introduce noise. Not sure on video.
You should be in manual. Aperture around 5.6.(This is what I just read doing a quick search on recording concerts.) Set Your shutter speed to double what your frame rate is. And you might have to do manual focus if auto focus doesn't work.
Hopefully someone with video experience will chime in soon.

Thanks Catherder. Yeah with Auto-ISO I know it's probably going to max the ISO. Not sure if I should take it off auto?? Catherder....why would I not want the aperture at its max(2/8) for the exposure?? Anything on what frame rate I should shoot at? Last month I shot at a show he was at, but only did still-shots. Some of them turned out really well I was nervous doing that lol. I shot in Aperture-Priority.

It said 5.6 for more focus area. 2.8 might be too narrow. Better to set iso so it's not changing. I would guess 24 fps, so shutter at 1/50.

Thanks everyone for the replies and advice. It was certainly a help, and is extremely appreciated. Just got home and pulled a few vids up and as expected I F'ed them up. Out of focus. Sorry for the less than beautiful language there, but I'm just extremely frustrated! Seriously just trying to help a friend I'm not doing this for profit. Now I got to message him and say sorry Bud I got nothing but junk! The audio is great. He's a hell of a musician and sounds awesome, but how can he use a video to promote his music that is out of focus. The frustration is because IDK even know why they're out of focus. They looked in focus while I was filming, obviously I wouldn't have kept shooting that way had I'd known. Sorry just Pi@@ed at myself. I didn't expect myself to become a professional videographer in one afternoon (that's unrealistic), but expected myself to get something that was at least usable/decent/semi-pro. It's disheartening when you can't even do that.