Purchased an 03 Civic Hybrid...seller assured me all necessary maintenance/repairs were done for car to be trouble free at least a couple yrs. He even said not to spend a dime on it after buying since nothing was needed & to call if anything came up in next few days. 2 days later, check engine & IMA lights pop up. I let him know & he has his mechanic pull the code which mentions the exhaust system, but no details/explanations. He says computer may need to be reset since spark plugs were changed & suggests we have the honda dealer check it out as well. Visited dealer for full diagnosis and discovered the IMA battery (probably the single most expensive part) was failing & needed to be replaced along with both catalytic converters...$5000 total! What are my options & how should I proceed?