By taxi
Its a one hour journey by cab. The cab might also not be able to pick up a passenger on the way back, so expect fares to be high. For comparison, the distance from KL to KLIA is about 80km and a one hour journey. Taxis typically want RM 70 for a trip to the airport. So you would expect something similar, or higher for this trip. You might be able to negotiate a good deal if you book the taxi for a return trip.
Hourly hire rates for a small taxi red/white is about RM35 an hour if you would like to book one for the duration of the trip.
By car
Make your way towards Sungai Buloh exit from North-South highway and follow the road signs towards Kuala Selangor. Alternatively if you are starting your journey from Klang, you can drive towards Kapar and head straight from there towards Kuala Selangor. Either way, the journey should not take longer than 80 minutes.