I have a stainless non-lock bolt shroud for a rem 700 short action.

I have a rem 700/308 stainless with the ugly-lock, bolt-shroud.

Is this a simple replacement task?

It is a very simple task. Call Gre-Tan rifles. I don't have the number handy but you can find them on the internet easy enough. I got the aluminum shroud to replace a standard and a j lock and I also got the fluted firing pin and spring assembly which makes it real easy.
The easiest way to do it is to get tool from Sinclair that makes the assembly removal easy. You can do it without a tool as Remington demonstrates but it is a little difficult that way.