If you have a 135K loan on an RV with 18 years left to pay it off what will happen if you stop paying if you don't care if they take back the RV and can they go after your other assets?

Assuming the vehicle is repossesed and sold to satisfy the debt, you will still be responsible for any debt remaining after the sale. It all depends on whether the vehicle is worth more than the remaining debt. If you are "upside down" in the loan you are liable for the difference.