I assume that, as you said, you will "...need to look into how to do it properly..." regarding the new drywall. There are various ways to do it. However, if you do use "slats" (furring strips) first and then attach the new drywall to that, you will probably be bringing the new all out too far to be able to deal with the windows and window trim etc. There are ways that the windows can be brought out to the plane of the new drywall, but it may be more work than you want to get into doing. And, it depends on what you have there now. The same is true regarding the outlets if you bring the new wall out too far. People do sometimes use furring strips when adding new drywall on ceilings, but ceiling usually don't involve trim and outlet issues except for maybe one ceiling light fixture.
Some people also go over old plaster walls with 1/4-inch thick drywall instead of 1/2-inch as a way of reducing the impact on existing window trim and baseboards etc. And, sometimes people just glue and screw the new drywall (whether 1/4-inch or 1/2-inch to the old plaster walls. If the old plaster walls have wood lath underneath the screws may hold to that, but it is also good to try to locate and hit studs that are under the original plaster walls.
As far as outlets are concerned, if you only add 1/4-inch or 1/2-inch to the thickness of the existing wall, there are outlet extenders that you can buy at Home Depot to bring to outlet box out to the level of the new wall. They call them "ReceptXtenders". Here's a link about that: