Way back when, you used to be able to acquire a "password" cracker from a third party. Don't know if such is still available for such an old copy of FileMaker. With it, you could use it on a copy of your file, open it and be able to determine the original password so that you can open an "uncracked" copy of the file with the original password and then remove this password if you want to.
If you get that issue solved, you'll want to read this knowledge base article before converting your file to FileMaker 11 format: http://help.filemaker.com/app/answers/detail/a_id/750/kw/converting
If all else fails, does the level of access you now have allow you to use export records to export data from the database? If so, you can at least export the data from your current database and then import the file into a brand new FileMaker 11 file--using the new table option in the target table drop down to both import the data and create a new table. This doesn't reproduce any of your exisiting layouts or scripts, but at least you would be able to access and work with the data from your original file.