848 belts are still two years or 15k. The bike has done less than 1500 miles a year so should tip the 7500 desmo service next year. There's no reason to pull the head covers early. Probably measure up within tolerance.
When was the last service tho? 6 months or 2 yrs? Of its out of warranty why worry? Maybe do the service at 12k or another year instead. The dealer os only telling you the cost of that service that is due: 7500
Agree with bradders took mine to Motorapido, service light came on at 7500 belts were not due for ages as only 18 months old they told me to wait until belts needed doing then do valve clearances at same time , had it all done at 9000 miles clearances were fine as Motorapido said they would be, belts, oil, filters, valve check, full body off check all over, chain, tyres and a full report at the end £600, very pleased with them.