Photographing a theatre production.absolute beginner

So I'm a real beginner in photography… Can get some nice shots and I have a good eye etc however, I've obviously only got an entry level camera (nikon d5000) and I ony have 2 lenses… One being the standard one i got with it - 18-55mm f/3.5-5.6G VR lens and Nikon 55-200mm f/4-5.6 DX VR Lens… Now i've obviously been researching lots of tips etc with the best iso levels and using spot metering etc but my I'm concerned my lenses arnt good enough… Will i be able to get any decent shots? Luckily my partner is the lighting technician, so a few days before i can go in before the rehearsal and get a good luck but does anyone have any tips based on my equipment? I can get my hands on a tripod if necessary.

A Nikon D500 is more than entry-level. Keep it at close-up/macro/flower icon mode and you will be golden!

Number one problem isn't the lenses, or the camera you have. The main issue that you need to worry about is not disturbing the audience, this is why my uncle and great uncle (who worked for the National Ballet of China) use Leica rangefinders, and Rolleiflex TLRs, because these cameras are considerably quieter. Your DSLR while being quiet will still be rather noisy, and pros will usually use a sound blimp to shoot this type of event. Since sound blimps are cumbersome and expensive (even to rent), I advise you to get some shots in during the dress rehearsals, this means you can use flash, and make noise without disturbing the paying public.

Your answer will depend on whether you will be taking pictures backstage or in the audience. If you are taking pictures backstage ("photojournalistic") then all you may need is a flash (preferably one which you can reduce the power and has a bounce/swivel head for "feathering" if you want to illuminate subjects at different distances from the camera).

If you are trying to take pictures during the play from the audience point of view, then that will be harder. You'll want to use the fastest shutter speed you can get away with. If you are using spot metering but don't want your subject in the center, then don't forget to lock your focus and exposure before recomposing your photo (read your manual to see if you can do this easily; if not, you may need to use manual settings). Since you will be further away, you'll probably be using the 55-200 lens instead of the standard one. This means a tripod will help (since it's harder to get non-blurry photos with telephoto lenses). If you can, you should also get a shutter release cable (since pressing the shutter with your finger can cause camera shake even if it's on a tripod)