I had one on my Cannondale road bike and it worked just fine. I never changed a battery so I don't know if the memory will be zapped if you do.

As long as you keep the computer within 45cm of the sender you'll be ok. The position of the magnet to the sender is a bit sensitive so you need to get it within 5mm or so. That won't be a problem on your bike. The 5200 is a Trek roadie isn't it?

FWIW I'd avoid use the 2-spoke magnet and instead use a single spoke magnet. That gives you greater freedom to position it depending on the fork profile and the angle of the wheel spokes.

If it's new, make sure you have everything in the box. My lbs ripped open a new one to give me a part I'd lost, and I don't know if they would have replaced it if they sold it to someone else. It's a nice 'pooter and reliable.