There have been several discussions on the topic (try a search)
But normally you need the following parts:
*BiP Subframe (steel) incl. rearset for passenger (you can probably find one on Ebay)
*BiP seat (complete)
*BiP heat shield
*New lockingpin hardware for your MONO seat (if you plan to use it with your "new" BiP subrame)
Making the change
It´s quite easy to switch over if you are moderatly good at doing mechanical stuff. It´s not complicated and any BiP subframe will fit your Mono, but try to get one from the same production year if possible. Your not saying what type Mono you have, but if it´s a standard 748 or a 748S, you shouldn´t have any problems mounting the ECU, which WILL be a problem if you have an SP, SPS or R model 748. (diffrent ECU = diffrent mounting points). Your Mono heatshield can be modified to fit a BiP subframe, but most seem to get a new heatshield instead of modifing the old one.
If you decide to let a shop do the work, it should take them no more then 2 hours to do the job. If you do it yourself, count on atleast 4 hours to be safe.
Once the change is completed, you may change your BiP seat to your Mono seat in less then 5 minutes.