How's the insulation?

You can learn how to fix anything on Youtube:CleaningPaintingScreen repairSome appliance repair Blow insulation in atticLight fixturesOutlet or light switch replacement Flooring (tile or laminate)Kitchen / bath faucetBathroom vanity and sinkReplace sump pumpToiletSheet rock repair (harder only to make it look good)Install dish washerDoor replacementWindow replacementKitchen cabinetsWater heaterShower replacementRoof (I have not done this)Garage door (I have not done this)HVAC (I have not done this and you need to be licensed in most cities)

Cats mark, so usually something that bad means taking out the bottom 4 feet of drywall (as in a flood) and putting new drywall up there - and maybe sealing the studs underneath before doing it, and/or changing out the insulation depending on how much saturation the drywall received.

If you try to insulate the walls it means cutting a hole at the top of each stud bay (the area between wood studs--usually about 16-24") and having an insulator blow in insulation. 

Part of addressing me the smoke smell for us was replacing the insulation in the attic and getting the entire attic painted white with kilz paint.

It indicates the top 5 improvements for 2022 were refinishing hardwood floors, new hardwood flooring, insulation upgrade, finishing basement into living space, and closet renovation. 

Another one to consider in addition to the mechanicals is the insulation...

A water heater has 2 "layers" the inner tank and an outer shell separated by some insulation.

Alternatively, they have insulation covers for the water.

That includes the wiring, the plumbing, insulation, egress, drainage, roof, and on and on.