I haven't had the chance to try a Toulouse saddle, but from what I hear they're decent saddles. $1500 sounds like a good price for a new one- it looks like $1750 is the going price on various web stores.
You can reuse the stirrups and stirrup leathers (although if the stirrup leathers are synthetic I'd recommend buying leather ones, as synthetic can cause excess wear on leather)
The girth depends on what type it is. Dressage saddles have long billets that extend down past the flaps, while jumping/close contact saddles have short billets the don't extend below the flap. All purpose saddles can go either way- if your all purpose saddle's billets are the long type you may be able to reuse your girth.