Despite being less than 100km, it’s a long old ride up from New Jalpaiguri or Siliguri to Darjeeling – about eight hours one way in all (and about seven on the way back). I did it many years ago and it was wonderful for a while but got pretty uncomfortable – I chose to get a shared taxi back (a couple of days later).
There are alternatives though: you could take a bus or shared taxi from Siliguri or New Jalpaiguri to Kurseong, from which it’s a three-hour ride in the train up to Darjeeling. Or you could even join it at Ghoom, 7km short of Darjeeling and the highest station on the line, from which it’s a spectacular 45-minute journey.
Also the timing is not very convenient. The train from NJP starts at 9 am, which becomes very difficult to catch if you are coming to city the same day from some other city. You may need to stay back in either NJP or Siliguri for a night to catch the toy train the next day. Taking a taxi or bus would be much more convenient to go up Darjeeling from Siliguri. However, if you want to experience the toy train, you can book either a morning or evening joy ride in Darjeeling, which runs between Darjeeling and Ghoom and takes about 2 hours. Check with IRCTC website to know more about the fares and other details.