Your bank is easiest.Any branch should be able to do it, but your own branch or another one where you are known to the staff may make life easier.Take i.d (passport or driving licence) and your debit card or cheque book.You'll need the SWIFT code and the IBAN number of the recipient's bank account. The French lawyer is highly likely to have provided those 'coordinees bancaires' , because they are good like that when it comes to getting paid!The bank normally asks for that bank's address too..If you get this done before noon you can have the money there by the next day , ( a priority service,at extra cost) otherwise it's a few days.
Cost? Ask, but when I've used priority to France it cost no more than c �60 flat rate. I've a feeling that it's about �30 or for the normal service, flat rate.