Tips on indoor event Photography?

Hey.
I’ve had my Nikon D80 for about….2 years, and I attempt to read the manual but it goes right over my head. I generally know only the basics.

I run my own event every 3 months, and have currently switched venues and it’s a lot darker inside than the last venue.

I don’t have a flashgun but I was thinking about hiring one out for the weekend of the event. Is this a good start? I don’t really like using a flash because it gives off horrible shines and colours, but I’m not sure what else to do?

I only have two lenses;
18-135mm
and 70-300mm macro

The event has quite a few different coloured lights too.

Example of the kind of lighting will be at this event (a photo I’ve taken before):

Thanks for the tips guys/gals

@Mad Luv
I’m both hehe, but I don’t usually photography indoors, mostly nature and portraits!
@Perki88

Could you possibly point me in the direction of which would be the best dome from the Gary Fong store?

http://www.garyfongestore.com/flash-accessories.html

That would be a great help, I never ever knew these existed so i’m unsure

If you rent a flash, be sure to use some sort of modifier such as a Stofen or Gary Fong dome. Here I have used the Fong dome: http://www.flickr.com/photos/perki88/2538748612/
Practice before the event.