Advice needed for a career changer

I have been working with an Australian developer for about 3 years by now with its Investment Management Business as an analyst. Prior to this, I have also had 2 years experience working in RE with other firms. The fund that I belong to is no longer seeking to grow further and is currently just looking into managing and monitoring the current performance of its assets. Hence, it is rather monotonous.

I am actually keen to consider a career change toward Investment Banking, particularly doing M&A. I do have to say that it is rather not easy to make this move given that most of my backgrounds are in RE. I do consider two things:

1. To start of as a 2nd year analyst at a boutique / big 4 group

2. Or to take internship program, such as the one offered by New York School of Finance or a seasonal internship program at boutique or banks

Any thought?

Thanks!