This is not an impossible task, since you have changed a water pump you should be able to do a fuel pump which is easier. Here are some steps to do.
1. First verify it is the fuel pump, there is a vent hole on the side of the fuel pump, it it is wet with gas, the fuel pump is bad, if it is not wet with gas, pull the oil dipstick out and smell it, if it smells of gas, then the fuel pump could still be a fault, and I would replace it.
2. If you can not see well, under the car, you need to drive it outside, preferable on the level ground. If you have to use a flashlight, it is okay, a led one is better, do not use a troublelight that has a light bulb, as since you are around gasoline, you do not want a bulb to break and cause a spark, as you will get some gas on your hands, and maybe down your arm.
3. Do not change your fuel pump to a 65 with the cartridge filter, stick with the 66 and use a inline fuel filter. If you can change the fuel pump from up above it is easier, but sometimes that is not always possible.
4. First step is to, plug the flexible fuel line from the frame to the pump where it connects to the pump, use a 5/16" dia bolt if you have a 5/16" ID flexible fuel line, and if it is a 3/8" ID flexible fuel line you will have to use a 3/8" dia bolt, so when you disconnect the line from the fuel pump, push the bolt into the line to keep gas from running out, maybe parking on a small incline might help, but I hate getting under a vehicle when it is not on the level. If you have any spills of gas, clean it up, before you proceed.
5. Next you need to disconnect the fuel line from the pump outlet to the carburetor or inline fuel filter, if you have a tubing wrench they work better by not rounding off the corners of the tubing nuts, if you don't have one then try the correct size wrench, if your fuel pump has an adapter fitting on it for the fuel line, you will have to hold it also with a wrench, but it does not have to be a tubing wrench.
6. Next, use a 9/16" socket (maybe a 1/2" socket), a 6" long extension, and a ratchet, and remove the two bolts holding the pump, then remove the pump, if the old gasket stayed on the block, then stuff a rag into the oblong hole the fuel pump lever came out of, let the rag stick out some, this is to prevent, getting gasket material into the crankcase, then scrape off the old gasket, a putty knife works well, then with the gasket surface clean, remove your rag.
7. Take the new fuel pump, and compare it to the old one, so that the lever looks the same, the fitting look the same size and are in the same orientation as the old ones, if they are then good. Use some gasket sealer and apply a thin coat to the gasket on one side and the fuel pump gasket surface, let it get tacky and then stick them together, being careful to line up the bolt holes. Then use like some chassis grease and coat the outside surface of the fuel pump gasket that will mate to the block, this will make changing it the next time a snap, no scraping on the block, and also put a thin coat of grease on the fuel pump lever that goes into the block, so the lever is not dry, when the engine is started, if you don't have any grease, you can use engine oil or vasoline. Then put your pump on the block and try to start your bolts, depending on the position of the eccentric on the camshaft that drives the fuel pump, you could have almost no pressure on the fuel pump, which makes installing it easier, to about 5 lbs of pressure on the lever if the eccentric is at maximum, if you have too much pressure on the lever to start your bolts, then bump the starter (you may have to pull the coil wire out of the dist and ground it to the intake so the engine does not start), so the eccentric is in a different spot. Once you get your bolts started, then tighten them down.
8. Then install the fuel line to the carb or inline filter, don't forget to hold the adapter if there is one on the new pump, you don't have to break the fittings, but they need to be good and snug, I would tighten them until you feel some resistance, then tighten about an 1/8 of a turn, all of these fittings are a flare fitting, which requires some pressure to make the steel on steel or steel on brass to seal. Then install the flexible fuel line, when you pull the bolt out, gas may come running out, so be ready on getting it on the fitting, then slide the clamp up and tighten it.
9. If your oil smells like gas, you need to change the oil and oil filter, as the gas has diluted the oil, and will cause accelerated wear in the engine, before you start it and drive it.
Then you should be good to go, Good Luck.