We have a small (8 section) basketweave fence that's been around for
40+ years. I recently reworked several of the panels using as much of
the redwood as possible and using cedar when I had to replace wood.

The post that holds the large gate has rotted at the bottom (was
repaired a couple times) at the top of the last concrete pour.

My idea is to use the original redwood post but to use a pipe to
secure the post. My thought is to place a concrete filled pvc pipe
into the center of the post, perhaps 3-4 feet deep, glue (or screw)
the pipe inside the post and then set the pvc pipe into fresh concrete
(again about 2 feet down).

I'm not a woodworker and don't have a horizontal boring machine that
could bore a 2 inch hole in the center of a post 3-4 feet.

I've thought of cutting the post in half then routing out the
material, placing the pipe, then glueing the two halves together but
don't know if I'd just be introducing another failure point with that
long joint and weather seapage, etc..

Any thoughts on how a layman could tackle this, or should I try to
find someone with a boring machine? (dont know what heading that
would be in the yellow pages)