1978 Ford Kencraft manual/expertise

Manual like this will cover the majority of the basic mechanics of the chassis.
Ford E350 Manual

Welcome. Always think of a motorhome as two separate units, the chassis and the house on top of it. Parts and manuals for the chassis should be readily available and my go to source is You tube. Search for your particular problem and most likely a mechanic will show you how to diagnose it. That year vehicle is more basic than the newer ones with all the computers and relays.

Above two responses are very good advice.
I hope you had luck fixing your motorhome.
Also since you may have an interesting item post a picture if you would I'd like to see it I have had 2 kencraft trailers before there are also boats under that name but not the same manufacturer

it is unlikely that you will find a manual for your motor home as such, but as one poster said , was you have two parts that make up the motorhome, the chassis , and the home, the find a manual for your chassis , Ford or GM for that part. Now for the home part try searching for each part, furnace, hot water tank , power supple/converter, etc that make up the home... I have a 1977 E350 chassis and a rollalong body, an so far have been able to find all the manuals on line from the various companies. all except for the master control panel and monitor, but with some reverse engineering have managed to make a working schematic of the panel that i can now work from..

Are you talking about the starter solenoid? if so there is not really much to it, from the start wire from the ignition switch it goes to the transmission neutral safety switch, from there to the Solenoid under the hood. the Solenoid is a common fail point have jumped many over the years in various Ford products to get home or to the parts shops. There is two small terminals one marked "S" other marked "R". R is the Ballast resistor by pass for the ignition to supply 12v for the ignition coil to give hotter spark for starting, the S terminal is the Start wire from the transmission safety switch, Jumper the S to the positive terminal of the battery should spin the starter. if the solenoid clunks and starter does not spin , using a jumper cable jump across the two large terminals of the solenoid and the starter should spin now, if it does, replace the solenoid, if it does not check the wire from the solenoid to the starter, if it good replace the starter..

I do not believe that information is correct. That is the way GMs work.
Ford has fuse links coming off the large post on side from battery. Other large post goes to the starter.
One small post comes from ignition, other small post goes through neutral safety switch to ground.
At least that is what I remember!

GM's don't have the starter solenoid under the hood, only on the starter its self, ford has one under the hood close to the battery, and may have a second on the starter its self

So apparently the problem is the lead hot wire from the selenoid not being a fusable link, which is the fix. We've successfully moved it twice, and it just needs the wire to connect the selenoid to the ignition in order for it to start, but to prevent a fire it needs to be connected each time the engine is started. Does that explanation make sense?

most auto supply shops have fuseable links, just have to know what size to get, or mount a fuse holder and fuse in its place, should be about 25a or so

Yes, it makes sense. If you can identify the amperage rating you could install a fuse.