Yes, you will have to add fat to the mix. Wild hogs generally have about 10% fat on them, and there is a very wide range of what it might taste like...from good (eating fresh grass and mast like acorns) to bad (grubs and carrion or swamp floor slime moss).
I highly suggest you take a slice of the wild hog fat and fry it in a pan BEFORE you grind and mix it together with the meat! This will let you know if it is good or you should trim it. Most times, the hogs we get, the fat is good....but every now and then, we have to trim it and toss it.
Also-make damn sure you remove ALL the glands.
Lastly, I shoot for around 25% fat when making wild hog sausages. But anywhere between 20-50% is acceptable. More domestic pork fat will tame the wild pork down a bit....so it's your call...