How do I replace this valve?

[LazyBoy]

Kubota B21 with BT751 backhoe, a pressure relief valve has rusted to where it's leaking badly on my main control valve,
it looks like it may just unscrew and come out, or do I have to disassemble it further to replace it???
And it's strange that one valve rusted badly and the others just have light surface rust?

 

[mcfarmall]

Looks like a typical cartridge valve. Should simply unscrew out of the manifold block.

 

[LazyBoy]

Thanks, I was hoping that was the case.

 

[beckmurph]

This is the valve body on my bh77.