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
Part link for all styles of GE Spectra glass cooktops ==> Cook Tops
Source: GE Spectra JBP78A0B2AA