You were covered under the falling object clause. Now they might want to depreciate that cylinder, but with a pretty new tractor, you are already eating your likely large deductible so they should just take the repair bill and pay it, less the deductible. Don you have the right to come back again if you find the first fix didn't work and there was more "hidden damage". Don't sign off on a full and final payment until you are sure it all works perfectly, nothing binds due to getting torqued around, etc. On something like this, one estimate from a reputable local repair shop should be fine.