Yes, spays for buns are very expensive. They are around $150-250. What you need to do is find a rabbit saavy doctor though. They may charge a bit less being familiar with the procedure and also be a better surgeon. The age I believe is around 3 months.
The panels are held together via zip ties. To make a door, just zip tie one side of the panel to the wall and use a dog clip to hold the door closed on the other side. If you keep the levels to a foot in height (about the height of one panel), the buns should be able to leap up to them without too much trouble. Make sure to put some sort of flooring on them though (such as cardboard or rug) else they’ll break a leg.
I don’t think she ‘hates’ people as much as she isn’t used to them yet. I’d try reading a book while sitting on the floor with her. She’ll come over to see what’s up. Just let her investigate – don’t pet her. It helps to get them used to you.