13 year old factory installed battery in 2004 Sebring

[riagri]

My late mothers 2004 Sebring lxi was built in June 2003. It was supposedly ordered with a class 1 hitch with correct harness voltage reg. Sadly she suffered a stroke in 2006 and passed in 2008. In June 2007 the check engine light came on. The code displayed 601, failure of the computer. The tech reset the code after a minor electrical unit was replaced. Its driven very little. The oil light comes on after warming up and stopping for light.Have only used 5W-30 since new changing the filter at every change. The tech noticed i have the original battery which is fully charged like new. Is this unusual. Also just found my oil ph.switch is leaking and must replace. Only 41,000 on car..I am looking for advice on whether to change the battery. Its a nice car but the computers failing worry me. Thanks