Piotr-

It appears you have learned the most important thing: You get good judgment by surviving bad judgment.

Your life experience with other "risky" activities shows that you most definitely have the maturity and experience to take a chance with an older high performance glider. Whether the Nimbus 2 is the right choice, I cannot say, but considering your willingness to look to others for advice, and your obvious willingness to actually LISTEN to that advice demonstrates that you aren't the type to just pitch your testicles out in front of the plane and try to catch them before they hit the ground.

Do some more research, talk to others and don't take any chances in the early stages of learning to fly whatever you buy. No nasty or questionable weather conditions, no charging off from the field on XC flights until you are completely comfortable landing at your home airstrip in a variety of conditions. Experiment (slowly) with high approaches, low approaches, extended patterns, abbreviated patterns, vary your approach speeds to determine your touchdown and rollout characteristics. In short, practice what it takes to deal with an off field landing before you HAVE to try one.

I say buy the thing. Inspect it carefully, get completely familiar with the cockpit and the controls and be really conservative in the first flights. And in all the subsequent flights, for that matter. Have fun, and remember that the one of the biggest rewards in aviation is flying as long as you can without anyone getting to say, "I told you so."