Glad you bought it Duck - I have been on the lookout for a shooter grade model 57 for some time. It seems that everytime one comes up, it gets snatched up before I can make a move (read that as permission from my wife).
Welcome to Club .41! Congrats on the buy; it's not often to get a second chance. PawnGal's recommendation on LAX ammo is excellent; they have a 210gr plated load @ 1000 fps. I've shot at least 400 rounds of it... much more like a .44 Special load than a .44 Mag, and nicely accurate. The brass is new Starline, so it's prime reloading fodder. Reed's Ammo & Research has several .41 Mag loads in stock, including a Gold Dot and a Barnes XPB load , a few .41 Special loads, and brass & components if you want to start with new brass. Enjoy the new gun!
You made a good choice finalizing the buy at $600. With the Pachy's on it you are ready to go shooting, and with the addition of a set of period correct Targets for an additional $80-$100 you will still be under market if you decide .41MAG is not for you and you want to sell.
You got some good advice here. Glad it worked out.