I did almost exactly as Vanguy said. Sanded with 120 then followed up with 220, wiped everything off, wood conditioner then polyshades bombay mahogany in one area and old maple (think it is discontinued) in another. It seemed to me that the old maple was easier to maintain consistency and was a little more forgiving. About the only thing I can add to what has been said is if you stain it in place be sure to clean up every spec of dirt on the floor or walls that your brush may come in contact with. If not it will be in the finish and with a gloss it will be very apparant. At the very least stain any trim pieces before putting them up too, pine is a pain in the butt to get good color into as you can see in the one picture.
The Old Maple (gloss)
Bombay Mahogany (gloss)