Buying a week on my NAVIGO. I struggled to get the cash-accepting machine to work until the ticket seller helped me. It is necessary to order all five zones (1-5) to get the week's worth of rides charged on the Navigo. It was 21.25€. The Navigo is good Monday thru Sunday and will now take you to Versailles and the two main airports plus other out-of-town destinations.
Trains to Versailles run every 15 min during the day. Monitors tell which track. The VICK train is the right one. It took about 45 minutes each way, plus the time on Metro getting to a RER C station.
IBIS hotel is across the street from the Versailles Chateau station. Rates looked very reasonable.
McDonalds has a super restaurant across from the train station, also. I stopped in and ordered my meal at a kiosk thing, paid at one counter, lined up at another for my food, then ate an excellent hamburger with fries. The place was jumping with students and others. I paid 7.30€ for a "meal," and didn't feel over-charged. It was the best hamburger I've had in a long time; the fries were perfect and didn't go stale after they cooled off. The bun was considerably better than what is used in the USA. At the far end of McDs is a coffee and pastry stand. They make smoothies and a variety of coffee drinks. The coffee (2€ for cafe au lait) was excellent. Next door to the McDs is a Starbucks and a TI. Neither seemed to be doing much business.
I walked about ten minutes to look at the chateau. Yup. It's still there. The fencing around it is unattractive. The place didn't look very busy at 11:30am on a Monday. It's chilly, damp, and early in the tourist season.