Depending on the size of your company and your registrar's requirements it might be nice to attend a training course covering the transition to MDSAP, but if you are already certified to ISO 13485:2003 and have transitioned over to the 2016 version (or are in the process of doing so) then you have already covered most of what MDSAP is looking for. The only additions are specific regulatory requirements for countries that your company sells medical devices to.
MDSAP itself will not replace your ISO 134885 cert, but it theoretically will allow regulatory auditor from Brazil, Japan, Canada, the FDA, etc. to all be satisfied by a single MDSAP audit report. Of course they will perform follow up audits on findings that score above a certain level, but in essence their workload will be minimized because the scope of their visit will be much more narrow.