802.11g vs 802.11n

Hello everyone. The church I go to wants to implement wifi and I'm not sure whether use g or n routers. A little info for you:

The church has a pretty large square footage (I don't know how much) so more than one router will be needed to cover the entire building.
They already have a wired infrastructure so no problems there.

Picture a long rectangular building. On one end of the building are the administrative offices. Right next to those is the chapel, and then on the other side of the chapel is a large gym. Initially we just want to have wifi on the end of the building with the administrative offices, but they'd also like the signal to reach into the chapel and into a specific room next to the chapel as well.

What I'm wondering is if the n technology is supposed to push the signal further out than the g technology, possibly making it more accessible to devices from a greater distance. I'm honestly thinking that we may need to use some sort of external antenna or repeater or something. This is where I get lost and need your help. Any thoughts?

tip #5 should be what you want.
http://www.microsoft.com/athome/setup/wirelesstips.aspx

All the tips are good ones.

http://open-mesh.com

N should, in theory at least, give better range than G. But to be honest, I think either would be fine here, it is walls that cause the biggest issues with range, and from what you describe there are only one or two walls to get through, so you may not need to do anything special at all to do what you want. I would just try in the first instance with good quality router, and see if it works OK. You can always add a different aerial afterwards if the basic setup is not satisfactory.

How about powerline Ethernet as an option using wireless powerline technology? Someone in another forum offered that as an option. Ever seen it in use?

It certainly can be a good alternative to WiFi. But there is one caveat - all the powerline adapters must be on the same electrical phase, or they cannot communicate. A building such as a church could be on either a single phase or 3-phase suply. I think it is more likely to be on 3-phase, which would make powerline networking unsuitable. Worth checking though.