This is really easy to do. First, you need to find, and get working, your lightbox library of choice. Once you have that work and you know how to access directly from the Javascript (ie, you know how to open the lightbox window from the JS code and you are not relying on JS listening to the onclick of certain classes) you just need to add that to a mouse event of the marker on creation by using 'e.target.options.title' to identify which is which and bam!
If you are not using an array for your markers, then you should do that.