First of all, I am not a plumber but a home owner, so take what I offer with that in mind. I am happy to report on what has worked for me, and will advise you similarly if a job has gotten beyond my reach. I am a former journeyman for a General Contractor, who is now one of my closest friends and have his advice to fall back on should the need arise...and to be honest it almost always has
That said....
With regards to the pressure balanced regulator. In my house this valve is inside the wall at every shower, and afaik, is only applicable to showers...since this is the scalding danger. I've never heard of a whole house regulator, but again I'm not a plumber just a home owner, with an old house and lots of home improvement projects under way? I suspect these are only needed on showers though, as this is the only place where pressure drops on one of the supplies could be dangerous.
Also, I'm not sure what you mean by "water tank." Are you on a well, and have a pressurized storage tank? Are you on a municipal water supply? What do you mean by water tank?
To the question about plumbers putty and a new drain cup. Your new drain cup will come with sufficient rubber gasketing, and if you clean the sink of debris and follow the install directions, which undoubtedly will call for a bead of silicone* I suspect the provided seals will be fine. I think, and several plumbers have agreed with me that plumbers putty is an antiquated product and I prefer to use a product which cures and adheres like silicone. If I were you I'd forget about the putty and apply a small bead of silicone to the topside of the sink where the basket flange will mate to it.
Good luck home owners, shade tree mechanics, and handyfolk of all stripes. I have been or will be there with you all in spirit. The most important lesson I have learned is that there is always a tool for the job, and the right tools makes things easiest.
And remember the two rules all plumbers live by: Shit flows down hill and DON'T BITE your fingernails
Best,
-bear
* I just reread the posting asking about plumbers putty and apparently your instructions call for this stuff. ~My~ advice, taken with what ever grain of salt you want is to use silicone in place of putty. As far as taking the old one off, there will be a large nut thread up the bottom of the basket, lefty-loosy this one off, and you'll soon realize how it is being held together. Look at your new one for clues about how the old one comes off.