Making bus reservation and which stop for W Trek?

Hello - Is it too early to make bus reservations from Puertos Natales to TDP? We are going at the end of November.

1) I don't see an email to make reservations for Buses Gomez. Does anyone know how to best contact them for seats? I need to make sure I can get tickets for 7 of us who will be trekking together.

2) We are starting off our trek by going from near Refugio Grande Paine to Refugio Gray (first night). Where do we get off on our bus to start the trek?

Thanks in advance for your help!