I'm sorry but you couldn't possibly tell where the leak is coming from with the description given. Coolant dripping from the undertray? Could be anywhere, coolant will always run into the undertray if it's from the engine and the engines cold.
The inlet manifold is a common place to get a leak, i've had one there myself. I've also had a leak direct from the head once straight after new gaskets all around and found the head to be cracked just under the exhaust manifold, had to buy a new head and have all new gaskets again. Both times it was dripping into the tray.
Mechanic or not, i wouldn't quote someone and get their hopes up that it's only a cheap fix when it could be something totally different leaking.
On this engine you definitely need to find the leak before knowing for sure what it is. Only take what people have said on this thread as suggestions so far, and then check to see if the leak IS in that particular place. Without a good look, no one can know where the leak is from over the internet.