threadwear, use the Trenitalia (Italy's national rail system) website:
http://www.trenitalia.com/tcom-en
While schedules will be reloaded for dates after June 10th, they usually don't change very much. If you know what day of the week you'll be traveling, just choose that same day of the week for a date prior to June 10 to see what schedules will most probably look like.
The fastest trains between Milano Centrale and Lecco are direct regionales taking around 39 minutes, and current prices are around 4,80 euro. You can very easily just purchase these tickets at Centrale on the day of your journey, no need to buy them in advance.