I made a similar repair on my Hunter 25.5. The compression post was rotten at the base and had to be replaced. So, I bought a new post at a woodworking shop that sold hardwoods. I got mine in Jatoba (brazillian cherry). Its just as durable as teak at half the cost. Only $125.00 for a 5 ft long 2 x 4. Anyway, loosen the shrouds, use a car jack and a 2 x 4 to support and slightly raise the roof under the mast. Pull out the old and in with the new. Retighten shrouds. I recommend using a hardwood like jatoba for your block as it will last much longer.