Are you going to actually remove the existing drywall?

If so, after the drywall is removed, the electrician will install the lighting cans (housing). Then drywall. Then paint. Then the lighting trim. Installing the trim is easy, so you may be able to do it yourself. Otherwise, the electrician will have to come back. If you do it yourself, make sure the electrician doesn't charge you for the return trip.

The other option is to leave the existing drywall intact and use remodel lighting cans. These can be installed with just a circle cut in the existing drywall. In that case, the electrician should be able to handle everything except for patching and painting the ceiling.

I purchased 4 Heath Zenith WD-9260 White Journeyman All-Metal Motion Sensor Quartz Lights from 3 different Lowes stores as they were on sale.
The last two I purchased were unlike the first two as they were constructed of a much lighter material and were approx. two pounds lighter then the other two lights.
They had a rough finish where the first two were heavy metal and were powder coated.
I would like to know if anyone else may have bought this same model light recently and found the same problem. I called Heath Zenith about this, but they unaware of this problem. Could these be grey market items?

Bames, write your own post instead of trying to piggy back on another post. Now, regarding the OP, remove the present fixture. Being an electrician, I have done this several times. Depending on how the entire fixture is made, you may end up with a large hole in your ceiling.

Next question, is your home one story? If yes, it will be a simple matter to use remodel cans and run the wiring in the attic.

IF, you have a two story home, depending on the can lay out, it may require cutting out patches of drywall to run wiring through the ceiling joists.

In our experience, most professional painters also repair drywall and do texturing if applicable.