all the bearings etc are on welded mounts on the plate...best to work out where those bearing are in relation to the hull...from what I remember and looking at plate K1 of the parts manual there are bearings to the left and right, and one straight ahead. Then cut the plate, drill the holes to bolt it on, and bobs yer uncle.
The bearings are fairly easy to take apart, but will most likley be OK, mine was a complete wreck (fire damaged), but the ring and bearings were fine...it was in a worse state than your one looks.
If you can afford the shipping I would check with banisters about the persiscope mount and gun mounts, he did have them a while back and the periscope mount does look a bit "weathered" on your one
Richard also had a huge batch of bump stops for the turret door made up, so you could also get those.
start soaking the hinges now