What are the timing marks on a single cam 1988 Chevy Nova 4 cylinder?

This is not an easy job. The belt runs around the passenger side engine mount. Now would also be a good time to change the water pump since it is also buried behind the covers. It's actually standard procedure at Toyota repair shops to do this. To change the belt, you need to disconnect the battery, remove all the belts that run the alternator, a/c, etc. Then put a jack under the engine and remove the passenger side engine mount. You will have to jack up the engine an inch or two to get at the 4 bolts that hold the crank pulley in place. The plastic covers come off next if there is nothing else in the way. This gives you access to the belt. Move the idler pulley out of the way (you will have to loosen the bolt a bit then tighten again when it's out of the way) and you can remove the belt. If you're going to replace the water pump, do it now (scrape off all of the old gasket or you'll have leaks). Make sure you do not move the cam or crank pulleys or they will get out of alignment and you'll have an even bigger mess on your hands. Put on your new belt, loosen the idler pulley bolt and it should spring out and put the belt under tension. The rest is simply reassembling everything else in the opposite order it came off. I didn't write all the little details, but this will give you a pretty good idea of what you're in for. It's almost an all day job, so make sure to give yourself a lot of time to tackle this.