You can view the [http://h20565.www2.hp.com/hpsc/doc/public/display?sp4ts.oid=3375953&docId=emr_na-c01039180&docLocale=en_US|Hardware Maintenance Manual] to replace the battery on the laptop.
Page 32 details the battery for the laptop itself
Page 54 details the battery for the RTC
The Hardware Maintenance Manual provides the full details for disassmebling the notebook if you are referencing a different part. You can use the [http://partsurfer.hp.com/|HP Part Surfer] to get the replacement part number for your battery. You should be able to purchase an RTC battery locally at an electronics parts or retail store.