If you are going to be replacing your CRM in a few years then this might be the big opportunity to overhaul and get GTD systems in place. But learning the GTD principles takes a couple of years anyway, so if you focus on the culture/habit changes now, and then when you bring in the software change later people will find the change easier.

Simple things, like identifying next actions at the end of the meeting, and getting everyone to write emails where they are explicit with what they would like the reader to do, could be really beneficial.