ETA: translate Oracle SQL queries to MySQL
Why are you migrating to MySQL?  Did you consider PostgreSQL?  I only ask because PostgreSQL is pretty much feature-compatible with Oracle, and would make a migration an order of magnitude simpler.

That said, translating 80 table definitions and 500 queries will probably take a month or so.  Simple CRUD statements will be limited to the expert's typing speed, but if you're doing any aggregation or other BI-type work it can take a day just to get one statement working.  You might be better off simply documenting every query then re-writing them from scratch using MySQL idioms rather than trying to translate them.