There are quite a lot of syntactical changes to do this sort of thing with 2.x, but most of the principles are very similar.
For example, here's some XF 1.x style code to open a link in an overlay:
HTML:
<a href="{xen:link test/page}" class="OverlayTrigger">XF 1.x overlay</a>
and here's the same thing in XF 2.x style:
HTML:
<a href="{{ link('test/page') }}" data-xf-click="overlay">XF 2.x overlay</a>
There are quite a lot of community-sourced XF2 development tutorials posted here at xenforo.com, but I think we're going to cover some 2.x add-on development basics in a future episode of
XenForo Insights, so keep an eye out for that.