OK. I'm not sure what to think of this "mechanic". Is there a way that you can find out what is so "complicated" to fix about this problem?
It sounds to me like he might just want to get it out of his hair. I'm assuming these components worked when you brought your car to him. I don't see anywhere in the things that they had done where it said anything about trying to diagnose the problem with your wipers.
It looks like they replaced pretty much everything in your blower system and also in your AC system.
Leaving your car out in the weather was obviously not a good idea and is likely the cause of the wiper and defroster problem you had. When an older car is exposed to extreme temperatures and moisture it will wreak havoc on the electrical system (and the rest of the car too). It's not your problem that it was stored outside and now won't work, unless they called you and told you to come get it because they didn't have anywhere to store it.
If the car was in their car after they fixed it and they left it out in the weather, and now it won't work, then they should fix it at no charge to you. This is what I would do if I were them.
This mechanic might be good at replacing parts, but I'm not sure that he knows how to diagnose electrical problems.
There might be something that I'm not thinking of so if you can get as much detail
as possible from him as to what is so complicated to fix. Also, I'm not sure why they didn't already have a wiring diagram. Any good repair shop subscribes to an online service that provides factory information (including wiring diagrams) for all vehicles sold in the US. I'm looking at the diagram for your car right now.
Anyway, if you can get me that info, I'll keep looking into this problem and see what I can do.