Bonjour CapnPitt 
Feel free to ask any specific questions and if you haven’t already found it try this site it has a lot of good stuff and deals with ‘jeans’ on a regular basis. .
Remember the metro is your best friend, it is democratically designed so that no one lives more than 500m from a station which makes it hard to stay lost for long ! IMHO it’s much easier to use than London or New York but one thing - no allowance is made for anyone with reduced mobility, when changing between lines you can walk for miles up stairs down stairs and up again.
Metro lines 1 & 14 have automatic doors but on the other lines there is either an obvious green button to push or a handle which you push upwards. The stops at the stations are plenty long enough for you to get out even if you’ve waited in vain for the door to open automtically - you’re more likely to find someone has opened it up before the train comes to a halt !
It might be worth your looking at the Paris public transport website there’s an English language version and a great route planner - you can familiarize yourself with the main transport possibilities from your hotel before you go. The carnet of 10 tickets sets you back about 10 euro 50 and usually works out better value than a daily pass especially as you can share them out between people.
Top tip - metro 6 is above ground for most of the route and you get some great views.
Ah the Taxi thing - well, it is true and it isn’t. You can hail taxis unless you are within a certain distance of a taxi rank. Ponster found an excellent site on taxis I’ll get hm to post a link tomorrow. The only tricky thing is working out if they are free or not - over three years and I still get confused, yellow light night fares in operation, white light free.
'French" style toilets (the French call them “Turkish”) are less and less common, should be no problem for a gent taking a leak and ladies just adapt the hovering technique you might use in a public toilet with dodgy hygeine 
Cultural differences - I guess what you might find odd is that it is up to you to tell the wiater what you want, once they have served you your food, drink you’ll be left pretty much alone until the plates are empty, forever once you’ve finished dessert.
Take as much time to people watch as do the tourist things, true a coffee is more expensive at a table than the bar but consider it rent - you’ll only be asked to move on or pay if the waiter is ending his shift or the bar closing up.
Paris is small too - only about 15km across so wear comfortable shoes and get walking. Some parts of 17th are seedy true but that’s as much Paris as the Eiffel tower and you’re not far from Montmarte.
Oh and you may want to wrap up warm we had snow today - the perfect excuse for the perfect hot chocolate in Angélina’s !