Bob-
The Yolo launch is very basic... really no services at all. Its an honor type system where you put $5 in an envelope and put the stub on yoru windshield. Sometimes there is a guy out there help to direct traffic at the launch but its very low key. However.. about a 5 minute drive north and there is a marina with gas, food, beverages, restaurant etc.
I'm trying to get the directions but there are none online, if you can believe that. I called a marina close by and they said the road is closed and the Elkhorn launch is being renovated. There is a ramp about 5 miles north of Alamar Marina (where they have the gas/food etc). It's called Verona. If you do a search you can find it.
Sorry... .its been a while, I guess things have changed.