Welcome to da club. You'll find there are quite a few Buick owners here too (even if the Park Ave or Lesabre is a second vehicle).
Oh, and for cruising or a long trip (Bonneville boys look the other way) Park Avenue Ultra w/Gran Touring Suspension >Bonneville SSE/SSEi with any of their suspensions. The ride quality of these Park Ultra'* is simply something that cannot be found in any American made car in the Buick'* price range in the 90'*.
For mods, I'd start with a CAI, some better plugs (NGK TR55'* or TR6'* after a few mods), better wires, smaller SC pulley (3.5 before cooler and 3.25" or 3.3 w/cooler), a little better muffler (probably don't want something too loud in a Park Ave), and a 180* t-stat.
Good luck and be sure to keep us updated on the progress as there aren't really any Park Ultra'* around that we know of that are modded (I managed to get my parents to let me put a 180* t-stat, CAI, and better plugs, and wires in their 93 Park Ultra -Dad is really coming to like the SC whine coming from the M62 and has note that the car has much improved response and 2-3 MPG more average).