Just walked out to my car last night and noticed a puddle of coolant under it. I lifted the hood and noticed the reservoir was about empty and the little plastic T up by the oil fill cap was leaking. I didn't have time to deal with it so I am still driving it as of now. I have not gotten a low coolant message yet. There is an open recall on my car about a coolant sensor. What do I have to replace? Is it easy or hard? The car has 82K miles now.