Hi Summerleft
While I do not agree with anyone taking "a sicky" if I were in your position I think I would do it. I believe that you want to try and make your way in the field of photography and if you keep having to turn down jobs people will quickly get the idea that it is not worth asking you to take their photos then what chance will you have??
I worked for over 38 years and in that time I never took any false time off and was rewarded {at the age of 55} with redundancy and to date have not been able to find another job. You are young enough to try and go for what you want in life and given the chance {in retrospect} I wish that I had taken the "Bull by the horns" and done what I realy wanted to.
As for the equipment you have WHY WORRY!!! everyone has to start somewhere and {as we know from the photos on this site} it is NOT the camera it is the person behind it that makes the shot.
Go for it and enjoy the day, WHO KNOWS WHERE IT COULD LEAD!!!
Regards
Sparhawk