3 Locations for what you require;
National Archives London http://www.nationalarchives.gov.uk/records/catalogues-and-on...
National Library of Waleshttp://cat.llgc.org.uk/cgi-bin/gw/chameleon
Record Office of Pembrokeshirehttp://www.pembrokeshire.gov.uk/content.asp?nav=2%2C107%2C14...
Wills for 1600 to 1858 for Pembrokeshire can be found for Free at the National Library of Wales athttp://cat.llgc.org.uk/cgi-bin/gw/chameleon?skin=profeb&...
1. Use the Diocese of St David's from the drop down menu
2. Wills of Pembrokeshire most wealthly families with land or property in various places or counties will more lightly be found at the E.C.C. of Canterbury held at the National Archives, which are not online.
Don't hold your breath with great expectations of what you will find and make sure your understanding of Latin is good to excellent.
ORIEL a welsh window on a surname