Yes - you are far too old. Give up right now and go get a pair of snowshoes and a Snuggy. :P
Anyhoo....I am senior to you by several years. I started riding park three years ago after more than 20 years on skis. Here is what I have learned:
1) I am not nearly as elastic as I was when I was a teenager. I have sessioned with many of the Oregon kids and watch in amazement as they stack themselves and pop right up with no ill effect or injury. On the other hand, I had a rather innocuous fall from a flat down box that has resulted in a shoulder injury that will probably require surgury. The upshot - take your progression slowly.
2) Pad up for jibbing - Though the kids make fun of me, I wear hard plastic knee and shin guards (661 mountain biking gear), Crash Pads shorts and jacket, helmet and mouthguard. I am too old to injury myself and miss work (plus I get more time on the hill if I am not recovering from injury). Last week I caught my tips trying to ollie onto a box and slammed my knee with alarming force. I bruised through the kneepad - without it, I would have shattered my kneecap.
3) White suburban teenagers are funny - NS kids think they look like gangsters and thugs and intimidate gapers. I think we look like gummy bears more than gangsters.
4) There is no substitute for the progression gained by hiking features repeatedly - I am up on Mt Hood everyday and have can essentially ride any park I wish. More often than not, I end up at Skibowl in the evenings hiking in the lower bowl progression park because I can get to it quickly from the parking lot. It is a lot easier to learn a new trick if you can try it once every minute hiking rather than once every 15 minutes from a lift ride.
Oh yeah - you will probably land on your head the first 10 times you try to ride a box. With people that are advanced skiers, every time in your life you have gotten into a sketchy position, you leaned back (into the hill) and it nearly always helped the situation. If you lean back on a box (and you will), you will end up on your hip and it will bruise horribly - it has litterally happened to each and every one of us on this site at some time or another. Think about sliding on a linoleum floor in your socks (better yet - slide on the linoleum floor first to get the feel you are looking for).
5) It is very important to know a few cultural things - particularly the appropriate response if someone askes you if you know how to get to Chad's Gap.
Go out and giver!