Flooring books may or may not help... try also the general purpose home books (the Big Orange Box has one called "Home Improvement 1-2-3", for example. It isn't very good for the subfloor part of this task, but has okay information about the plumbing and finish floor side of things.) If you don't already own one like this, I'd suggest you get one for everything else you might want to do around the house. There's no perfect category of trade for this job. Part of the complication is that plumbing usually requires a license, so you'd be taking a bit of a chance to have an unlicensed individual working on the plumbing. If you go to a plumbing company, they might have carpenters that they use, but it'll cost a little more for the coordination they have to do. If you approach a general contractor, they'll have the carpenter and connections to plumbers, but they might also view this as a small job and upcharge you for the bother. A handyman without a license to do plumbing would probably do an okay job, but there's a possibility that they'd botch it. If it was me, I'd try and find a combination licensed plumber/ handyman. You'll pay a little more for the plumbing ticket, but it may help you sleep better at night. My gut tells me that this would come in under $2000, but there are too many unknowns to even call that a guess. (And double that if you live somewhere really expensive, like California or NYC.) Get a couple of people out for a quote. Ask for proof of liability insurance and call their insurance company to see that they're currently covered. To drag you back to the DIY side of things, if you feel competent and safe with a circular saw and a drill, and own basic plumbing stuff, then I think you can do this. Double that vote of confidence if you have another bathroom in the house to use while this one's being wrecked.

Just wanted to add that it's great that your contractor is preparing the subfloor correctly. In our new house, the subcontractor didn't take the time to level the concrete substrate, and ever since we moved in we've had a problem with boards not sticking. Eighteen months after we moved in, we finally had enough and hired a certfied NWFA inspector who found that there were variations in the flatness of the substrate as much as 1-1/2" over 6 feet. Now most of the floor is going to have to be pulled up and the concrete leveled and new flooring put in. We're not happy and worried how the newer flooring will flow with the existing, not to mention the mess that will be made in our new home.

anglophilia- I'm sorry your husband died of cancer. However, that does not mean that since he he didn't die of an asbestos-related disease what you did with your floors was necessarily safe. Maybe it was, maybe it wasn't. Many people have exposures to toxic materials, even multiple ones, and it doesn't cause them health problems or kill them...but some are affected. In my posts above urging caution, I'm not suggesting that if you have an asbestos exposure it will kill you...it's just that you want to minimize avoidable exposures. I have a 93 year old relative who is still alive after decades of smoking and working around asbestos, and I also know of a 30-year old who died from asbestos exposure as a result of a several week summer job he had in college. Risk is a complex issue that depends on many factors, including genetics. One can't predict which individuals specifically will come down with a disease from a certain type of toxic exposure; we can only see what the overall incidences are and try to help people avoid taking risks that might make them one of the unlucky ones. We are all exposed to nasty stuff, often without realizing it. Typically, larger exposures --- such as occupation-related ones -- are more concerning. But there are some substances, such as asbestos and lead, where the medical and scientific communities have yet to find any level of exposure/intake that is guaranteed safe. People want risk to be black and white: it will kill me or it won't. But most environmental concerns aren't like that, so we have to live with a wide spectrum of gray, and make personal decisions on how cautious to be or not. I know for certain something will kill me some day, but I try to avoid making choices that will possibly speed that up....

Sounds questionable. Variations from 2 to 3 inches are rare. Chances are you don't have them, but even if you did, putting down parquet wouldn't disguise them. Get a long straight board and/or a level and set it on sections of the floor. Making a blanket statement about all concrete floors being out of level is inaccurate. The parquet in the unit was probably done because it was an inexpensive wood floor, not to deal with a subfloor issue. Floating floors are very sensitive to level however. They generally use the same specification as architects which is level to 1/8" within 10'. Humps in the floor can cause areas to be bouncy. This is generally easily fixed by doing some floating.