Metra is the commuter rail system in the Chicagoland area. The train to Crystal Lake is part of the Union Pacific Northwest line. The station by the hotel is the Pingree Road station, not the Crystal Lake station.
The fare between the Pingree Road station and downtown is $5.55 each way Thursday and Friday. Saturday and Sunday, you can purchase a $5.00 pass for unlimited rides. If you're bringing family, each weekend pass allows 3 children to ride for free.
If you're coming as part of a group, a 10-ride booklet of passes may be cheaper for you.
Directions to the hotel are straightforward - in fact, you can see the hotel from the train station. If you'd rather not walk it (it's about 3/4 mile), sign up for a ride on the Arrival Schedule page.
The red line shows the path out the parking lot, along Congress Parkway, down Pingree, to Tracy Trail, and to the hotel. The yellow line shows a slightly shorter path that requires walking along a little path to Pingree Road.