How to prove that "Total" is not recursive (decidable)
A set $A$ is recursive iff $A$ is recursive enumerable and $A^c$ is recursive enumerable. You know that $Halt$ is recursive enumerable but not recursive so $Halt^c$ must not be recursive enumerable. You can show that $Total$ is not recursive enumerable (and therefore not recursive) by showing that it is reducible from $Halt^c$.

Formally, to show that $Halt^c \leq_M Total$ you need to find a total computable function $f$ such that $$x \in Halt^c \Leftrightarrow f(x) \in Total$$