1) is it relatively easy to sell a property without using an agent or solicitor? You don't need either, but of course finding a buyer is never easy, especially now, so an agent can be very helpful. There's really no need for a solicitor, but you will need to know what documentation to have prepared, and be happy to deal with stuff like changing utility contracts and paying your plus valia etc. If there's an agent, they will help with all that.
2) once a buyer is found, what are the normal steps that are taken - a) ask for a deposit to take it off the market, b) both sign a purchase contract, c) organise a date for completion? I'm not sure that there are any "normal" steps as such. It will be pretty much a case of what you agree with the buyer. If the buyer is in a position to complete immediately (e.g. cash buyer not needing mortgage approval) then it can all be done very quickly - basically as soon as the buyer or his solicitor has obtained a nota simple from the land registry and made an appointment with the notary. You will need to obtain certificates from the town hall showing rates are up to date, and from the community if applicable showing fees up to date, and (if you are a fiscal resident) a certificate from hacienda, which may take a couple of weeks.
3) should the deposit be keep in an escrow account? If so, how can this be arranged and via who? Or is it normal for the seller to keep the money in their account? Again, whatever you agree with the buyer. If you can get a deposit yourself, great, but the buyer may prefer his lawyer to draw up a private contract and hold the deposit. If there's an agent involved, they may hold it (in lieu of their own fees, naturally!)
4) for a property selling for €214,000, what would be a suitable amount for the deposit? 5-10% is probably what an agent would tell you (to ensure he gets his fee!), but in a private sale, since the seller will hardly incur any expenses prior to completion, any amount purely as a gesture of intent may be acceptable; a few hundred, a couple of thousand, whatever. I've sold in the past when time from agreeing a price to signing at the notary has been one week, so didn't bother taking a deposit at all.
5) are there standard purchase contract and deposit documents that can be found on the internet that a private seller can use? There may well be but I'm not aware of any.