Changing the fuel filters is about the same as changing the oil filter. As I remember, the main filter is pretty straight forward. I poured the fuel from the old filter into the new one The fuel/water seperator is another story. When I purchased the fuel/water seperator I purchased another bowl (amber cup on the bottom) and assembled the pieces(make sure that you have all of the gaskets in place that are supplied with the new filters). Be careful when you remove the fuel/water seperator as fuel will keep running since it is gravity fed so you need to be quick when changing it. I know because it caused quite a mess the first time I changed it. I purchased a large filter wrench at an auto parts store since the filters are larger than normal auto filters and they can be quite tight from the factory. As for tightening, make them hand tight and then tighten about 1/2 turn after that and that should be sufficient. After changing the filters, you need to turn the key to the on position (on position- not start position) for about 20-30 seconds and then turn it off. You will need to go through this cycle several times to get the filters filled with fuel. After this, the engine should start up ok. I have not changed the air filter as yet. If you go under the rear of the coach on the drivers side (opposite the oil-fuel filters) and look up, you will see a large black cannister. That is the air filter.
If you need anything else, let me know and I will see if I can help you.
Tom and Margaret
2014 Berkshire 390bh-60