Graphics Driver Questions

I have the following HP:

http://h20566.www2.hp.com/portal/site/hpsc/template.PAGE/public/kb/docDisplay/?sp4ts.oid=5187022&spf_p.tpst=kbDocDisplay&spf_p.prp_kbDocDisplay=wsrp-navigationalState%3DdocId%253Demr_na-c03359127-12%257CdocLocale%253D%257CcalledBy%253D&javax.portlet.begCacheTok=com.vignette.cachetoken&javax.portlet.endCacheTok=com.vignette.cachetoken

For the past few weeks, I've been researching in order to upgrade my Graphics Card and PSU. I  guess the Intergrated graphics is disabled when a discrete card is installed? I just upgraded the driver for the APU a couple of days ago. For my particular model, what is the best way when installing the discrete card and its driver. Would I need to unistall the  AMD Catalyst manager prior to installing the new card? I read that with the models using Win 8( I have Win 7) that the BIOS would need to be adjusted. Would that be the case with my P7-1235? According to the HP website, there are no upgrades for the BIOS for me.

Thanks to anyone in advance for your advice.