Can i or the current owner be sued for fill dirt that is across property line

The economics will be decisive, I am not sure how easily the home can be moved and what that will cost. One thing is certain, if it can be cheaply moved, it is way cheaper than lawyers. as to who is liable: the new owner is first in line especially if the home was sold "as is (meaning he is on the hook for this not you)." If it wasn't depending on the warranties, title insurance may cover it as may some home insurance policies. If the new owner reaches out to you on this, splitting the cost of moving might be cheaper for both of you rather than go to court. The neighbor might sue to have the mobile home moved and the fill dirt removed. Why he sat his rights for so long might be an issue. The fill dirt might be deemed a trespass or nuisance but, since it has been there 10 years, any claim would require the neighbor to have just learned about it for those claims to stand much chance in court. Also the extent of the nuisance will depend on visibility of the dirt to the neighbor, the cost to remedy and its interference with his quiet enjoyment of the property (did the alledged nuisance interfere with how he lives in the property?).  Next, the placement of the home 8 feet from the line might trigger enforcement by the municipaility. If you can get the municipality to give a variance for the impropery location of the home, that would be one way to solve the code issue, or moving the home. You have some homework to do, get some estimates, check the sale paperwork