The service manual also has special tools listed that will press a bushing out with just wrenches. Like gear or pully pullers, it's just a threaded rod and sleeve setup, but ideally sized for the arms and bushings. I picked a kit up several years ago in anticipation as I knew I'd likely have to do the job eventually, but also because I wanted to collect as many of the dealer tools as I could while they were still more available. Don't think it even cost that much, but if you aren't one who likes to work on your car to begin with (or can't for whatever reason), then I guess that doesn't really help.
40 hours does seem on the steep side to me though. That's 10 hours per corner, but I guess the bigger question might be what all that includes. Actually taking the arms off and replacing bushings is likely not that long of a job, but I could see some padding built in for stuff like stubborn bushings that might need to get cut out or something like that. Still though, I would think a capable shop could do that in a day's work. What might be included in that 40 hour quote would be aligning the car as well. That can take some time to get right, though modern equipment does make it a lot easier. I've spent many hours in my garage trying to get my car dialed in, but that's also just me working in non ideal conditions taking my time. I'd still say it shouldn't take any more than a single work day to get it done, if that. So all told I would think 20 hours seems more than reasonable, but then again I'm not a professional shop trying to cover the cost of my tools or anything that might go wrong. I've had 5 minute jobs take 5 hours and jobs I thought would take hours like pulling an engine only take 30 minutes because I've done it before and know what I'm doing.
It's hard to really estimate without looking at the car and actually getting into it, but a pure sanity check for me is 40 hours is a full work week. Do they really think they need your car for a full week to get the job done? Granted, multiple people could be working on the car to make that faster, like one guy pulling arms off the car while another replaces the bushings, but that's still 2.5 days if two guys are doing it. Still feels long to me for that kind of job, and you can only throw so many bodies at one car to make things any faster.
