E.P.
Yes, it's good that they stained it but... there are so many brand names and some of the swing sets have better hardware on them. Sounds like a cool set and it seems like it has a few unique features so you may be able to locate it on-line.
How is it secured in the ground? Like previous post - check if it is cemented.
Sounds like an awesome set - I always go by the rule ---"he who names the first price, loses!" theory... If you say $200 and she becomes totally offended - you've lost. If she says... $100, you can always come back and say "Oh, that's too low, how about $150??? Win/win. If this were my swing set, I'd have an idea of how much would be a good offer to see it leave. To have someone else disassembling it - that's probably worth a lot to her.
I love bargaining but I wouldn't want to offend anyone. Also... like your previous post said, she MAY want to rid herself of it MORE than you want it. Definitely a bargaining chip there!
Good luck.