Hello all. It's been a bit since I've been through the forums due to being so busy the last few months. I've not had much time for recreational photography.
Recently I was asked to be the journalistic photographer for my church's General Assembly that is held annually. This gathering is an assembly of all the churches from around the world to conduct the buisness of the church for the next year. Thus it is greatly important to have good photography work for the visual record keeping and memory of the event, not only for the sake of the church's history but for print publication afterwards as well.
I was asked on short notice and was greatly short on equipment to meet the needs of the enviornment. The auditorium has very low lighting and it is also a very large auditorium as well. Probably in the neighborhood of 25,000 to 30,000 square feet total.
My plight is this... As stated above I was underequiped. I knew I was but my experience and the late timing made me the best man for the job. As a result I have been asked to do the work each year and I am going to have to invest quite a bit of money into getting some great equipment. I have a 20D and right now I have the standard kit lens. I was fortunate enough to find an 85mm Canon lens from a friend to use this year (I have just returned.), which wasn't as good as I need but it helped a bit more than the 55mm kit lens for the shots that required a closer profile shot taken from off stage.
I have a few quick thoughts as to what I would need but I'd like to get some suggestions from the more experienced, professional photogrpahers in the audience. I'm sure a flash, a telephoto, a few small fixed lenses will be on the list but my use of more specialized lenses is limited. I use a 70mm - 200mm zoom on my job and the standard 28mm - 55mm type lenses. Any suggestions of any equipment I may need is greatly appreciated and welcomed. I'm in grave need of a working list of the proper equipment suitable for the enviornment as I need to begin planning on next years work. This time next year I want to have exceptional results from the trip. 
Thank you all in advance. 

