I found where the power switch connects to the motherboard under the Keyboard, but it was an effort to work out how to remove the keyboard cover (tip: the manual is confusing, pry the cover near the hinge and not between the keyboard as pictured).
Computer screen still stayed blank but I eventually worked out that my RAM was causing the problem, no beeps so it was hard to tell what was going wrong. Put in working RAM and it booted fine.
While I was searching for the NV54 service manual I came across a few posts which claimed there was no service manual - but there is one on the Gateway site if you search hard enough.
here is a link to it http://tim.id.au/laptops/gateway/gateway%20nv53.pdf