The gas station is closed and will be for quite a while.
Coming from the west you can see Half Dome at a distance from a turnout called Portal View on 120 as you head down into the valley. This will be after the point where 120 goes left at the gas staton and heads up to Tuolumne Meadows. Once you are in the valley you can see all the hot sights.
If you choose to turn left at Crane Flat and continue on 120 toward Tuolumne Meadows you will get a great view of Half Dome and Clouds Rest from the Olmsted Point lookout.
If you choose to go into the valley then after you have made the loop there you can go on up to Glacier Point stopping at Washburn Point which is very near the end of the road to Glacier Point proper. Continue on to the parking lot at Glacier point and walk out to the point itself and you will have a pretty close look at Half Dome. Vernal and Nevada Falls still have some water going over. Yosemite Falls is dry. Bridalveil also has a little water going over.
There is some road work going on in the valley and you have to pay attention to the signs directing you towards highway 41 and Wawona. The Glacier point turnoff is about five miles after the Tunnel View turnout. You should stop there for a photo op.
If it were me I would go to Glacier Point via the valley loop if you are coming from the west. If you get to the valley floor by 2PM you should have time to do the loop and get to Glacier Point while the sun is still up. The moon will probably be coming up around sunset or so.
Old Dude