It is quite a process replacing spark plugs on ‘09 Honda Fit. Before you start thinking about it, make sure you know how to remove - without damage - several parts from above the firewall. You need to remove wiper arms, plastic trim parts under the wipers, than the whole wipers linkage has to be detached and propped up, … plus another large piece of sheet metal beneath wiper linkage assembly has to be removed, …  all that to get a half-arsed access to harness, coil packs and spark plugs.

At that point you still will have to be quite ambidextrous. Some things can be only handled with a right hand, … some other with a left, some with both, … and some with wishes for a third hand. All hidden from sight by that plastic valve cover. A good mirror on a handle will help. It’s all doable, … but you have to watch yourself for sharp sheet metal edges, … than you have to reassemble it all!

As to a fuel filter, it’s part of the fuel pump assembly, all mounted in the fuel tank. Access to it is by removing a centre console, … just beneath the emergency brake handle. Once the centre console is removed, you will see wiring, fuel lines, etc. You will see a circular plastic ring. After disconnecting wires and fuel tubing, you unscrew that plastic ring and lift the fuel pump/filter assembly, … than you have to reassemble it all!

F.S.

https://www.youtube.com/watch?v=7hJh4e9GaCo&feature=emb_logo

Plugs and coils are easy. You can get to those by just removing the cover you saw.

But the fuel filter is, unfortunately, in the tank and you will have to drop it to replace it.