Unless you have no money to pay someone to do the work, it's always better for landlords to hire out the repairs. Property owners are not entitled to money for doing the repairs yourself.
Was the tenant responsible for the yard maintenance as part of the lease? If they were and didn't maintenance the yard, then you are entitled to the money.
If you were paying a gardener and the lawn is damaged, the tenant is unlikely responsible because the yard maintenance was not their responsibility. The gardener should have told you, the yard is getting messed up because they are parking on it and you could have taken action at that time.
If you do the work yourself, you charge $340 because that is what it costs. Keep the receipts.
If A sod cutter, dump fees, and pallet of grass will cost around $340