How to Import Data to MySQL RDS Instance?
When we did something similar recently ~250GB, we first used an EC2 slave from production database as a staging slave with SSL and binary logging enabled  -- to make table dumps, etc. Converting any tables to InnoDB if you need here. Load data dumps from EC2 to RDS. Then used a binary log feeding strategy to load data and keep it current. At cutover time, flush the last binary log-- and load it into RDS and you're done. I prepped the logs first (removing any set cmds that require super) and just fed them to the mysql client on rds. Next time I want to try Tungsten replicator.