where S^2= sumof(xi-xbar)^2/(n-1)

I tried

var(s^2) = E[(s^2)^2] - E[(s^2)]^2

I have already proved S^2 is unbiased estimator of sigma^2

so

E[(s^2)]=sigma^2

hence E[(s^2)]^2= sigma^4

Can anyone give me hint/tips about how to find

E[(s^2)^2] for N(u, sigma^2)

if i do

var( sumof(xi-xbar)^2 / (n-1)) then I expand

= (1/(n-1))^2 var(sumof(xi-xbar)^2)

I have a dump question here,

does var of sum = sum of var here?

Thanks