Hi Mark,
You need to stop thinking about drill bits firstly!

Look for a data recovery company. If the data is as important as what you say, you probably shouldn't attempt to play around with it.
DR pros have quite a few tools that can work with damaged drives, but every operation you do without knowing exactly what you are doing can either increase the chance of losing the data forever, or increase the cost of recovery or both.
There is a very good chance they can recover your memories.
You can take the drive out of its external case and try and run it in a PC, though if it is a Western Digital Passport, it may be encrypted.
You might see some problems on the PCB if you take it apart, you should check under feet/stoppers and lables for screws, or simply prying it gently apart with a spudger.
once it is apart, take some pics and repost some details.
but my strongest advice is to go to a Data Recovery company.