He had bought it 41 years ago (built-in 1965) and did absolutely nothing to it but throw on some carpet on top of the hardwood floors and clear out a wall to make the living area/dining room feel a lot bigger.

Probably 2 long, parallel onesBathroom 7000Replace flooring with LVP (waterproof kind), if vanity can be saved - save, sand and paint, replace counter top with manufactured quartz, replace sink, replace plumbing, replace faucet, replace lighting, replace bath pan with new fiber glass panand tiles around the shower area (builder grade/might bump to 1 grade higher)Flooring @ 2$ a sqftSave, refinish hardwood flooring in main bedroomHVAC175 a pieceinstall new window units if current ones are not functionalLighting and fixtures 1000Replace with new ceiling fan and down lightWindows already included from unit 1Reglaze if not too bad condition, replace if damaged/beyond repairStair area 1500Replace stair with laminate, replace door going from unit 1 to stairwell, paint stairwell area, replace window on top of stairwell areaGas line 175InpectCasita total $13425.00interior 1500remove old paint, tape float repaint - agreeable greyDoors 250Save if possibleCabinet 750Save if possible/ Sand & Paint/ replace where neededHood range 250Vent to outside of the houseUpper Cabinets 500Remove current cabinets, replace with floating shelves.

Is it ever worth it to use a carpet cleaning service, or should I just rip it all up and install new carpet/hardwood.

@Chris K. why not just do hardwood?

I'll need to pull up some carpet and refinish hardwood floors.

Seems to me you would want to have some of the hard wood down prior to showing people, but I understand the desire to get some people in there.

Mostly hardwood on the main floor, 2 carpeted rooms.

Personally refinished at least 14 old hardwood floors, then tons of cabinets, countertops, doors, you name it. 20x return all day and no haul away or inevitable problems the retro fits always have. 

If it is more of an adult area, than engineered hardwood has a higher end feel and still durable.I would go medium toned as too light will show all dirt, dust and crumbs, and too dark is not in style.

I had a contractor refinish my hardwoods for me and he finished 3 days ahead of schedule and did a fabulous job.