I did a similar sort of job, early last year, installing 6 chopper fans in a local Church here.
We used a scissor lift for the job and I must say that the whole job from start to finish was a real PITA.
All of the pews had to be removed, the scissor lift barely fitted through the doors to get into the actual part of the Church where the fans were to be fitted and we had to get large sheets of Plywood to make sure the Lift didn't fall through the timber floor.
It took 4 times longer to do anything in there because the exposed Timber and steel bracing members in the building were always in the way of the scissor lift and the multi-core control cables (thankfully black) had to be clipped out of view.
Safety was a huge thing in the job as well, I didn't like the idea of using a scissor-lift in the beginning, but there wasn't really a lot of slope on the floor after all that and it was well within the Lift Manufacturers specs for topple over.
Personally I hope I never do a job like that again, it actually took us twice to 3 times longer than what we thought it would.