$\displaystyle X(t)$ is a Gaussian stochastic process with mean $\displaystyle m_{X(t)}=0$, ACF $\displaystyle r_X(\tau)=\frac{1}{1+\tau^2}$

Determine the expected absolute deviation $\displaystyle \epsilon = E(|X(t+1)-X(t)|)$

I have no idea where to begin except maybe setting $\displaystyle Y(t)=X(t+1)-X(t)$, but then I have to figure out what the PDF $\displaystyle f_{Y(t)}(y)$ is and I'm not sure how to proceed.