If your engine is visibly leaking oil, you should remove that cover and try to find the source of the leak. But this is not something a typical do-it-yourself mechanic can fix, its possibly you will need new gaskets or worse (such as cylinder rebuild, or worst case replacement of a cracked engine).
It is just clipped in. Just pull up - it will snapp off.
there are 3 5mm Allen nuts in the front. these are easy. the weird part is the back. there is a Toyota symbol in the back center. twist it counterclockwise till the shield is released.
If it has 1 then it is located behind the plastic cover on the front of the engine.
Right in front of the hood latch in front of the radiator. Under the plastic cover. their are two horns side by side.
On the front of the engine inside a plastic cover with a 27mm "nut"
on top of the engine in front of the turbo under the plastic cover
I have a 3.5L engine. Remove the silver plastic cover plate over the engine (2 nuts up front, hinge in back). Facing the engine, it is in the front right corner under the cover you just removed.
on the front of the engine behind water pump (water pump is bolted to it )
PCV valve is located in front of the engine, behind plastic (long and narrow plastic cover that covers valves and fuel lines). You need to remove one hex screw that attaches plastic cover to engine and remove plastic cover. You will see pcv valve 3-4 inches to the right of the hex screw that was attaching plastic cover to engine. Once removed you will see silver pipe at the end of the pipe plugged in engine sits PCV valve. PCV valve plugged into engine by it's mettalic side, so only plastic side is visible. Easiest way to understand how PCV valve sits is to buy new valve in auto parts store, remove plastic cover that covers fuel lines in front of engine and find a part that looks like PCV valve.
It is located underneath the plastic engine cover on the right side of the engine as you look at it from the front.
It is located at the front of the engine below the top radiator hose you have to remove the top timing belt cover to get to it.
You remove the large plastic engine cover from the top of the engine (remove the three plastic caps, then loosen the three 10mm nuts). It's right on the front top of the engine under a plastic cap about 3" in diameter.