I have had the distinct displeasure of having to replace 2 stanchions on my 2005 310 and it wasn't fun. I had to replace them becasue they were bent by the weight of the ice and water that collected in the gullies of my winter cover. I suspect that your leak may have been caused by a similar phenomena.
One of my stanchion was in the V-birth and the other in the cabin. Initially I also assumed that there were glassed in backing plates but I can assure that on my 2005 310 there are not. There are simply washers and bolts. With a little bit of luck, when you remove the outside screws some of the washers and bolts may very well stay in their original spots due to the calking around them. This happended to me about half the time and made it a lot easier to get the screws back in. By the way, the screws are not all the same size so pay attention to where each inserts. Half of the nuts and washers, however, fell off when I removed the outside screws.
In the V-birth, you first need to remove all the molding and the side panel. To remove the side panel, a screwdriver with a flexible shank may help. However, for most pf the screws you do not have enough room and you must cut some access holes in the headliner in order to insert a screwdriver. I did this with a Dremel tool. Fortunately, when you reassemble the wood, the top molding will cover the holes in the headliner. Even after removing these panels it will be very hard to see the bolts but they are there. Then with a myriad of wrenches, curved tongues, needle nosed vice grips, etc, etc. you will be able to remove the bolts and replace them. Hope this helps a little
Jeff.
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