Contact the seller again and explain about your attempt to retract your bid.
Ask for a Mutual Cancellation. If he agrees, accept the MC immediately and leave positive feedback. "thank you for helping a newbie" would be appropriate.
If he does not agree, he can as noted, open an Unpaid Item Dispute which gives you a Strike. Most sellers have automatic Blocks on bidders with Strikes making it much more difficult to bid and buy on eBay.
