The address of the venue is -
Stade Pierre de Coubertin
82, avenue Georges Lafont
Métro Station: Porte de Saint-Cloud
Yes, I think the qualifying rounds are played at Stade Coubertin too! (and I'm not totally sure, but I don't think you have to pay admission for the qualifying)
I've been to the tourney for the last two years but I usually attend from the wednesday onwards, so I don't know about the ticket situation on the monday, but going by the rest of the week - usually all of the Category 1 seating is sold out before the tourney.
But you should be able to just turn up and buy a Cat.2 ticket which allows you to sit anywhere in the upstairs seating area - though you aren't right at the side of the court, you can still get a really good view from anywhere in Stade Coubertin!!!
Anyway, I hope you have a great time, it's a really fun tournament to attend, there always such a good atmosphere and everyone is always so friendly!!!
If you need any other info, just let me know!!