I would agree with this but it's true for any platform you move to. The people who use Linux on the desktop don't have to know anything about the switches for administration and you would have to invest in training regardless of which platform you move to. Also, there are graphical tools to perform most common functions of administration on the server but the important thing to remember with Linux is that once it's setup the odds are high that you won't have to touch that setup again unless you want to add or remove functionality. Being able to work with office documents and even having a fileserver takes as long or less than working with Windows. Like anything you should research it well but, for what you want you don't need to know that much more as a user, however, you should have someone you trust who knows how to work with Linux and can even train you on how to perform basic administrative functions for the server. One of the pluses with Linux is that
everything can be scripted and scheduled if you know what you're doing so your consultant can just come up with a script that you can run for various common functions.
There are all kinds of issues when you change platforms including incompatibility, training, and support so in all likelihood you'll need to create a relationship with a support consultant and spend a great deal of time learning about day to day administration until you have an understanding but once again that's the case regardless of the platform.
Some other possibilities to look at are virtualization software which would allow you to boot another OS at any time without having to restart your computer. Microsoft's Virtual Machine is completely free and supports Linux but not Mac (http://www.microsoft.com/windowsserversystem/virtualserver/software/default .mspx) .
I think one of the most important things to remember as "Fuller, Theron K Mr" mentioned it should all be about what does what you want the best. To me this is not just truth about platforms but even life. I digress.
Right now there is a growing movement of people who claim that Macs are the best just like many of the proponents of Linux did and do regardless of the situation. It's clear that the arguments are less about functionality and more about social statements. In Linux's case it was about sticking it to the man (Microsoft) and the case of Macs it's about lifestyle (I'm this kind of person and this kind of person believes that Macs are best so I believe Macs are best) Apple has a great marketing department. 
Assess your needs, discover the best way to meet them, decide if the change from your current situation to that other "better" situation outweighs the investment (time, money, opportunity cost, etc). But keep an open mind at the beginning and you'll be much more likely to find an option that fits your situation more uniquely.
Hope that helped more than it confused.
Joe
-----original message-----
>>;I'd pretty strongly recommend NOT looking at any open source tools unless you have a paid expert on your team to support those tools! A customer of mine recently sent in their "documentation" for their brand new Linux installation - it was 75 page manual of command line prompts for administering the server. Terrific for someone with a strong background in Linux / Unix administration - but not supportable at all for a small nonprofit.>>
.