do i have a strong small claims case ?

In order to form an enforceable contract, there must be consideration exchanged on both sides.  You haven't indicated that this third party, whoever he or she is, received any consideration, i.e. anthing of value in return, for paying for the repairs. Sometimes consideraiton is not required if you deterimentally and reasonably relied on a promise.  This is known as promissory estoppel.  If you only got the repairs done in reliance on this promise, you may have a claim.  However, it will be difficult to prove that you only had the repairs because of the third party's promise to pay.  Also, some judges may not think you suffered any loss, because you did get your property repaired, and it is now presumably worth $2,500 more than it would have been without repairs.. As far as any clqaim against the seller, you may have a claim, but since his/her agreement to pay for repairs was oral, it may be difficult to prove it.  Also, if you have a writtten contract, any alleged oral representation which contradicts it is likely to be barred.  This is known as the parole evidence rule.