Ammo is the easy part, Winchester AA, Remington STS or the equivalent from just about anyone would work fine. Most of these will be target loads so you will probably be limited to 7 1/2 at the largest. You might find larger shot sizes with the European brands but you probably would need to order them. RST deals with light loads for older guns which might be more applicable. They are kind of pricey but may be the only option if not a reloader.
Chokes are tougher, I reload so would probably pick IC/Mod and change loads to open things up. I might go that route anyway as I would rather have tighter than more open for desert quail and even for grouse.
Picking a recoil pad is tough. I have no brand loyalty so would pick the one that I thought looked best on the gun. How the gun balanced compared to my preference would also be a factor as I would pick a heavier pad to lighten up the barrel balance or a light one to keep it as is.
