How difficult is it to create an iphone app?

While I don't consider myself to be an expert, I feel I know more about technology than the average person, and pick up new information and skills easily.

At work we wanted to start using a survey application, but none of the ones out there have the functions we need.

I've been thinking about trying to make an app for our organization that does what we need, but I don't know how much work that would entail.

For an iPhone, you need a Mac computer. You download the Xcode IDE and then support for the new Swift programming language - DON'T even consider using Objective-C, Swift is so much better and simpler in more ways than I can describe in this short space.

Once you've got the support in place, you can start working your way through on line and other tutorials.

A word of caution. Coding for mobile devices is more complex than coding for desktop computers. If you just wanted a desktop application then I would simply say download the Netbeans IDE and learn Java from a text book or online resources. You would end up with an application that will run on (just about) any Mac, Windows or Linux computer, but of course it wouldn't be "mobile".

Finally, you may know that Java is also used to program Android devices. Even though the language is Java, you can't easily convert Java desktop applications into Android apps.

It depends on how well you are able to learn a new language.
The language most common and recommended language for learning how to make an iPhone app is Objective C.

I'm currently undertaking a programming course myself. From my own experience, the iPhone is the most advanced mobile operating system and is definitely the easiest to develop for only if you understand the programming fundamentals and concepts first, and then the objective C and Object oriented environment.
I recommend taking a look at lynda.com
It will have all the resources you need to develop apps etc.

I recommend these three courses:
Foundations of Programming: Fundamentals
http://www.lynda.com/JavaScript-tutorials/Foundations-of-Programming-Fundamentals/83603-2.html

Objective-C Essential Training
http://www.lynda.com/Objective-C-tutorials/Objective-C-Essential-Training/143328-2.html

iOS App Development Essential Training
http://www.lynda.com/iOS-tutorials/iOS-App-Development-Essential-Training/159179-2.html

If you don't want to pay you can get a quick start here without having to subscribe as long as you know how to torrent (at your own risk legally speaking):
Foundations of Programming: Fundamentals
https://thepiratebay.se/torrent/7901458/Lynda.com_-_Foundations_of_Programming___Fundamentals