Is it possible for an older person to overcome ageism and succeed if they have the skills?

Yes. Like all forms of discrimination, you can take some skills or actions to stand against ageism. You have to speak up. In all kinds of gatherings where people of all ages can be found, you might tend to be in the shadows and watch, but don’t be afraid and try to participate.
Ageism can be easily defeated by staying mentally and physically active. Follow the news and stay tuned. And more importantly, display this information to your people to indicate your awareness of what is happening these days. Use social media and email to show your family and friends that you can communicate like them. If you presume that you can’t do some particular things because of your age, you actually won’t be able to do them.
Age is not something that can stop you from anything. Try to do your daily shopping and go where ever you want. Hang out with younger people or be present in places that younger people can be found more often, like gyms, clubs, bars, etc. This can transfer the energy everyone gets among more youthful people to you and motivate you to stay positive and active.