It will be fine, dont panic! but you just have to take cash from them when they come to collect.
All you need to do when the auction ends (if they win it) is to contact the buyer, and swap details with them, agree a time for collection etc.
After they have been and paid and taken it away, you can mark the item as "paid" and then "despatched" on your selling list.
My advice when selling is do not leave feedback until the buyer does. As a seller you can not leave negative feedback if you come across a twatty buyer (and believe me there can be some).. you can only leave positive feedback.. but this can be done cleverly in a way to alert sellers that they might have problems with the buyer. Not that you can do much about it, but if other buyers check out your feedback, they can look at your buyer and see both sides of the story..
Do NOT accept paypal when someone is collecting an item from you. The reason for this is that if a buyer were to say that they had paid by paypal, and not received the item, paypal will ask the seller to provide tracking proof of postage. If you cant provide that (and if they have collected, you wont be able to), they will automatically give the buyer their money back. You will then have lost your money and your goods, and there is nothing you can do about it. Paypal will not accept a signed receipt from your buyer when they collect or anything like that.. they want official royal mail tracking numbers or couriers references.
But you will be fine..good luck with the auctions. :)