I'd try to find a good eventing trainer. Going out and doing recognized events isn't something to take lightly, and the way you jump XC is very different from the way you would aproch a stadium fence.
Eventing is VERY expensive once you get competitive. You need show clothes (coat, shirt, stock tie, pants, boots, gloves, helmet, whip, spurs, xc vest, watch) and tack (dressage and jumping tack, boots for your horse, probably a breastplate) and little miscallanious things that you never think about but will need (a metric wheel, tack box, wraps, extra hay nets). If you do go into it seriously, there is alot of equipment that comes along with showing and traveling.
Eventing is what my trainer did, so I did it. And I love it. You truly have to know your horse inside and out, and you have to know yourself and how you ride too. There's alot of mental game that goes with it (which is where a good coach comes in. There's nothing better to me than a good pep talk from my coach right before I go out of the XC start box). And there's nothign better than hearing the starter count down the 5,4,3,2,1, clean start have a nice ride! Seriously, it still gives me chills and an adrenaline rush every time.
Good luck with it all! Eventing really is the best horse sport EVER! (not biased or anything :P) You are garunteed a tough, but fun time