麽40歲的男人 is still young，從IT轉護士is a good choice

But you probably need to spend 3-4 years to get your RN license. Usually, you can go to a community college to get in a two year RN program. Before you can get in the RN program, you need to have some prerequisites, namely have credits from related courses i.e. biology, etc. You will be then to be put into a lottery system or waiting list till your lucky day is coming. You will need to be very careful even after you are in the RN program, you could be kicked out for whatever reasons, i.e. the instructor believes you are not fit into the program either by your test score or your hospital precept.

By the way, my wife got her RN when she was 51, after she finished the two year RN program. She told me she might be the oldest student in the class. In fact, the most of her classmates are younger than our son.
But she did know quite a few students were over 40.
My wife works for a very good hospital. The starting salary in the area for a new RN is close to $45/hr, and in one or two year, you can get over $55/hr

I would like to say "go for it"