98% is a meaningless number without knowing their feedback total and reading the feedbacks they've received.
If they have a feedback total of 100, then I'd be suspicious and move one. If their total is 55,000, that's not so bad.
Go through the feedbacks and look at the negatives. 9 out of 10 times, it's someone who bought something expecting perfectly new and w/warranty but the listing is for an 'as is' or 'untested' item.
Double-check to make sure PayPal covers the item if it's not as described. Also, make sure the seller either requires insurance, or at least offers it.