Behind the plastic shield is the timing belt and water pump. As for the check engine light, you need to get the code from autozone or the dealer to really identify what the issue is. I think the trans fluid you are seeing is another issue...unless you are seeing A LOT of it.

It is possible you have a powersteering leak (same fluid) or a line to a transmission cooler is leaking. Neither one will throw a CEL.

Get the code and we can go from there. Did it ever go back off?