Carpet replacement is straightforward—the main decisions are material quality and color. For resale purposes, neutral colors are safest. For living comfort, personal preference matters more.
Timing consideration: carpet installation is disruptive. Coordinate with any other work that requires moving furniture (painting, etc.). Ideal sequence: paint first, carpet last.
The upstairs wood floors being in great shape is a significant asset. A professional cleaning will make them shine without the expense of refinishing.
Square footage matters for accurate estimates. Measure or have contractor measure before committing to quotes.