Yes, you are too old and should never, ever do anything new ever again.
Really though, what a strange question. Of course you're not 'too old'. You will never be too old to learn new things. In fact, you should strive to learn new things right up until the day you get hit by frozen urine falling from a jet passing far overhead. Anyway, you're only 47! Why are you talking like this? It's entirely likely that you will live for another 40 years, or more. Unless you smoke that is, in which case you can cut that expectation in half unless you quit. :0
From a less philosophical slant. If you have a programming background then learning ROR will be an enjoyable synch. All of the difficult things are done for you and you're forced to do things in the correct way. The best approach would be to buy a book and sit down and learn. Don't try and guess things like so many people visiting this forum, if you spend a couple of week's evenings working through a book like agile web development with ror then you'll be set. It should be an enjoyable experience, full of those moments where you laugh to yourself how clever something is or how nice the ruby syntax is.