Hi - All Manx wills are on public record. Those prior to 1911 are available at Manx NH Library or ordered for inspection at any LDS Family History Library on microfilm. Order up indexes first.
Later wills through the Registry of Deeds at Deemsters Walk in Douglas up to 2002. There is a fee of £1.40 per will inspected after 1910. All this is explained in the Manx Family Tree. Try buying a copy.