When I adopted Sandy, she was around 6-7 years old, and almost totally potty trained. I took her out every 20 minutes and she learned that was where to go potty. I also enrolled her in an adult training class where she learned to come, sit, and stay as well as walk on a leash. She has also learned a few other tricks since the class, it is a bit slower than teaching a puppy but all she wants is to please me
I'm a big believer that you CAN teach an "old" dog new tricks, my Sandy is proof of that!
Good luck with your new one - I'd love to see pictures!!