You can upgrade your Lumia 525 from Windows Phone 8 to Windows Phone 8.1 within an hour. But you must note that once you installed the newest version you can't downgrade it to the previous one and it will void any warranty available for your device until the original version launch.
How to install Windows Phone 8.1 developer version First of all you need to sign up for the Windows Phone developer program which is completely free. Just visit the page appstudio.windowsphone.com to signup as a developer. After the successful signup process click on the Start Project option available in the right side of your screen. Then go to Windows store and search for the Preview for developers app.
Download and install the same. Then open the app, agree the terms and conditions, click on the enable preview for developers. Then go to the settings > open Phone Updates and search for new updates. Now you can see a new update available for your device. It should be noted that it's not the Windows Phone 8.1 update. It's only an update which is available for your Windows Phone 8.0. Install this update. It may take half an hour or more for the update and installation process.
Again visit your Phone update page in settings and check for updates. Now you can download the Windows Phone 8.1 developers preview. This update may also take about an hour or more. The first update can be done by mobile network, but the second one surely needs a Wifi connection. This second update needs around 700MB data for installation. I am sure that you're going to love your updated phone.