Hi,
For data, it is easily possible to import CSV files into collections.
Limitation is, 1 file has to be less than 12MB, so you might need to run the migration process multiple times.
If the data is huge, it should be possible to do it by setting up SEC + JDBC adaptor to read directly from existing database into RMP.
Process design has to be re-written. It is fast and easy to draw the process on RMP, it should not be majority of effort.
In-flight processes migration is very advanced topic, and needs to be carefully planned, and be executed exactly and precisely as designed.
Basically, you will re-generate the workflow instance and move it to correct step. There are APIs to move process systematically, or you can design your workflow to accommodate migration.
Best regards,
Taka