Parking, Watching, Eating
You didn't say from where you are driving into the city. If you are coming in from NJ and taking the Lincoln Tunnel there is a garage right there when you exit (I think it might be on 42nd). That's probably your cheapest bet. You then walk a few minutes to the Port Authority subway station and take it one stop downtown direction to Penn St. 34th st. You don't even have to exit the 34th st. station to make your way to The Garden.
This EXO is local for me but I really don't like this fake stuff. And I can't think of a less interesting match-up even for a fake match. But to non-tennis people, which will be most of that crowd at least courtside, they know Roddick.
That said I've spent hours just watching Fed practice so I certainly see how you want to see him play even a fake match. When he leaves the game there will be a whole as large as any player that's ever left it.
As to the seats, in my opinion the upper section at the Garden is not really good for tennis but I remember sitting up there sometimes back when they had The Masters and I had a good time.
If you do go, enjoy yourself. And if you are looking for a bite after I would steer clear of that neighborhood and walk over East a few blocks to 32nd between 6th and 5th. A ton of good Korean restaurants and most are open very late (I believe some maybe 24 hours). And a cuisine you will not find on the V.I.
If you go, let us know what you thought.