The only masts I've seen done at the dock
involved boats with a tabernacle. We have half a dozen Grampian
26s with 32' masts but they are deck
stepped, and have a tiny little shoe on the bottom of the mast which gets a hinge pin in it. The lads use a 10 foot pole with a couple of plates at one end that fit the hinge. The pole is attached to the hinge, and projects flat along the deck
forward from the mast. Its upper end is attached to the spar with lines and the mainsheet is then used attached between the pole end and the bow fitting. The lower forward shrouds are let go, the upper is slacked off a tad and the rear lowers are left as is. This gives support to the stick as it pivots aft. You end up with about 20 feet of mast stuck out over the stern rail. Its fairly easy.
My boat has an 18 inch high tabernacle and the pin goes thru the mast. I also use a pole about 10 foot long. The plates at the end go around the mast and the hinge pin holds it. It projects forward parallel to the deck and the end is attached to a strop secured just below the spreaders. Then my mainsheet is attached to the end of the pole, and the other end to my samson
post. Same thing, gently lower away. Only in this case you end up with about 25 feet of mast over the water
. You need a few people to sit on the butt end when you pull the hinge out or the mast will upend and go down off the stern end.
The secret in both of these is that the butt end of the mast is always controlled. Its never free to move except along the fore/aft line.
In your case it appears that you are deck stepped but have no hinge. So if you are going to use shear legs, you will need to attach the lifting tackle to the mast at just above the center of gravity so that it is balanced. Once that is done, you should be able to lift
it an inch or so and then walk the butt end forward while lowering away on the lifting tackle. Since you must release ALL the standing rig, You will need a couple of people to walk the mast butt forward, and a couple to keep tension on the lower shrouds as the mast comes down so it doesn't start moving from side to side.
It can be done, thats how they got spars into the hulls of large sailing ships. Just be verrry careful.