If you were referring to replacing the "cook Top"

it's pretty simple....

turn off power

open oven door

remove the 3 or 4 screws that hold the top down in the front

raise top up, use a board or something to securely hold the top up

as you will need 2 hands to remove burner assemblies.

burners should be mounted on plates, remove the entire plate

with burners attached carefully laying them down.

repeat with rear burner assembly

now the top is ready to remove.

Normally it just sits on the hinges in the back,

there shouldn't be any screws holding it on

but you may have to look at the hinge closely

to see how the top needs to be manipulated to

remove it.

Part link for all styles of GE Spectra glass cooktops ==> Cook Tops

Source: GE Spectra JBP78A0B2AA