How many computers are too many?

The church/school my family and children attend are considering creating their first full time IT position. (Currently, there are a couple of computer hobbyists sharing the load with no formal training.) The school has about 40 computers, including 1 lab and the church has about 12. There are 2 servers. There is also talk of another lab being created bringing the total to about 75.

The O/S’s are a mix of WIN XP, 2000, and some 98.

There is also talk of have the person teach tech courses at the school. (MS Office, C++, etc.)

What does the community think? Is this too much for one IT guy?