Nethaji,
Q1: Yes. You can use the Import and Export features of Metapedia to bulk move terms. There are also web services that could be used to extract terms. Any more automation to load would require custom ETL/ services to insert data, which may cause issues. I believe there is a change coming to import terms from PowerDesigner.
Q2: Yes, MM will version the differences in the database. Metapedia and MM can be combined by linking terms to objects, but you cannot create in Metapedia after auto creation (not without a custom DB trigger). You could build a universe to merge information and track changes required.
Yes, changes to sources are captures in MM.
regards
Adrian