I've only ever sold brand new items on eBay and never second hand, so I'm not so familiar with the pitfalls of second hand.
I can give some general advice however. You can say in your listing that you will not accept bids from buyers with a low feedback rating. You could set a minimum standard of 20 or 25 rating and 99% satisfaction, or whatever you're comfortable with. This should rule out the majority of scammers and time wasters. It might also rule out a genuine first time buyer, but if you're selling something worth several grand you can't afford to take the risk.
As for postage, I wouldn't insist on personal collection unless you're really worried the buyer might want to return it. The main obstacle might be weight though, so it depends on how heavy it all will be. Prices for parcels in the UK have never been cheap, but I've been shocked recently by how much the cost has gone up. Weigh up your total package and see what the cost is at the Post Office (there's a price chart on their web site). There's maybe not much point using a courier company because unless you are a regular customer with an account they'll likely cost more than the Post Office will. That said, a courier company may offer better insurance terms, which sounds like it could be important given the price tag of the items.
If you are using the Post Office then Special Delivery is A TOTAL MUST. This has insurance, but you will need to check what the limits are and you might need to buy a higher level of insurance if it doesn't fully cover it. Definitely make sure your items are fully insured and fully tracked in transit.
In general, swap some emails with your buyer, you can judge quite a lot from this and the time wasters and pernickety arses are quite easy to spot. If you sense trouble, walk away from the deal, you are under no obligation to sell, you just issue a refund (if they already paid) and tell eBay you've withdrawn the item because it is no longer available. You'll lose your listing fee of course, but nothing worse, it won't count against your rating.
In terms of when to list, it is usually best to ensure your auction ends at a weekend, either in the afternoon or evening when the most people will be around to bid in the final stages. Definitely set a reserve and perhaps also consider a high Buy Now price to secure the really keen buyer who can't wait and also give other bidders an idea of where you want the price to end up. Unless your item is a surefire seller, I wouldn't gamble with a no reserve auction.
Good luck!