Coolant leak in #5 cylinder

[glindy]

My 2000 Ranger 4.0 leaks coolant into #5 while sitting,and causes misfire when pushed hard while driving and first started.I used coolant sealer and it stops for a while,but starts up again.
Is it coming from a lower intake leak or would it be a head leaking coolant into cylinder? These is no coolant in oil. Plus how long does this repair take or how much would a shop charge to fix?
Thanks

[tomboy]

Could be a head or head gasket, how much $$$$ and time will depend on the shop.