can anyone give me advice on how to stop a 5 month old golden retriever from wrecking my lawn.i have a 3 year old one as well but he is fine.any remedies would be appreciated.

Provide him with a digging pit; hide toys/bones in there, and therefore he can satisfy his urges without ruining your grass.........

Get a large (200ml) syringe and fill with water.
When he starts to dig in the wrong place squirt a syringe of water at the top of his head.
No pain, no injury and a very puzzled dog with a wet head results.
he will find it disagreeable and will not easliy associate the 'punishment' with you.
It is an effective and gentle way of moderating unwanted behaviour.
You should only need to catch him three or so times, he will learn very quickly.