The top set of steps are fastened with bolts from under the engine cover platform. Feel for them through the insulation andcut a small hole to remove them. There are also 2 bolts into the top of the steps that are under the aft cabin mirror. To remove the mirror for access to those top bolts, you dig out the wood plugs that hide the mirror screws and remove the mirror.
After the top steps are removed, you are on your own to identify how the engine compartment top is removed.
Personally, I would try to access the injectors without removing the top of the engine compartment. I don't think all the effort would be worth the better access.