While reaching NJP, you can find certain Tour operators outside the station. Go directly to any registered one (avoid pimps), and ask for a customised package. They provide the cheapest and best deals, I have visited thrice like that.
Day 1 - Reception of tourists at Bagdogra Airport / NJP railhead. After refreshment depart for Yuksom. Reach Yuksom in the evening. Transfer to hotel. Overnight at Yuksom. Day 2 - Half day sight seeing in the morning including visit to Khechepalri Lake. Back to hotel for lunch. After lunch drive to Ravangla . Day 3 - Local site seeing during the day. Overnight at Ravangla Day 4 - Early morning drive to Darjeeling. Darjeeling Sight seeing. overnight in Darjeeling Day 5 - Darjeeling Sight seeing. I think you should squeeze in a day or two more in your trip