I have been lurking on this forum for a while, and have finally registered just so that I could respond to this thread and say a couple of things that I think have been neglected. (I'll introduce myself on another one rather than hi-jack this one.)
1) Think twice about buying an instrument on eBay. You know nothing about horns. With a seller that at least does not completely mis-represent things you will see the dents and scratches, but you will not know if the valves stick, how the horn sounds in comparison to others, how freely it blows, etc. I think you said you had a friend who was a trumpet player. Let him or her help you find a horn, try it out, offer opinions on more than one. Yes, with a highly reputed seller you might find a good deal on eBay or even on craigslist on one of the "can't go wrong" models that have been recommended here, but do be aware of your own ignorance and keep your eyes open.
2) Many people have urged you to start learning to read music. I can't disagree, but if you want to be able to play by ear and to improvise you'll need to practice that also, and it is a different set of exercises. I learned to read music (as well as I do, anyway) at a relatively early age, but did not understand what was required to learn to play by ear, and at times I still feel like I am "chained to the dots" - unable to play unless I have the music in front of me. Put on a blindfold if you have to. Play along with recordings, the Abersol sessions, "Band-in-a-box", or whatever, but if playing by ear is one of your goals don't neglect practicing that also. And don't be surprised if it does not come as easily as with a diatonic harmonica, where pretty much all the notes "work" because the instrument is more or less all in the same key.
Best of luck!
(And enjoy Ottawa if you end up there - I lived there a few lifetimes ago.)