The Deposit Account (Post Office Savings Bank) gives you easy access for lodgements and withdrawals.
www.statesavings.ie
If so, you fill in a form - it's on that page! - to request a "repayment" and take it to the Post Office. Then they send you a cheque. You'll get it a week or so later. I'd imagine you'd then be waiting for said cheque to clear when you deposit it.
Or, you should be able to take out €3K a day in cash over the counter. So you'd be done in less that two weeks; probably the same time as getting the cheque and it being available in your own bank account.