[jarrus]

too much meths will eat your fuel lines, but most cars use corrosive resistant fuel lines (i forgot what the material is, nylon comes to mind but I don't think it's that)

also in the how easy is it bit, you need to work out how much meths and soda lime to add and if you are using clean veg oil then there is a set amount which works, but on WVO then you need to titrate some of it to determine the exact amount to add, however i'm sure there are biodiesel systems that will do it for you though,