Doors and Windows - extension jambs for a seated 10' bow window

I am at the point of my project in which I need extension jambs for my 10'X5' peachtree bow window. There is already trim on the window, but the window sets in approximately 1 inch in the wall. It is a five panel bow window, in which all windows open up. One question I have is, because the trim is already nailed in place, do I have to remove it so when I put the jambs in place, the trim molding will be even with the molding going around the whole window? Also, should I hurry up and stain the interior wood of the window immediately, or can I wait until, say, winter for me to do it. I have to still put the siding back on the house where the window is and a thousand other things on the honey-do list. Any help is greatly appreciated.

Yeah, you'll have to remove the interior trim to install the extension pcs......I never seem to get one that will line up close enough to the old interior mouldings to even let me use them....though sometimes I can cut 'em down and re-use.....

I'd think the finishing coating could wait til winter without any problem......if you don't have LoweE glass in them and the sun hits the seat board a lot of the day, you might want to cover it with something like butcher paper to keep it from "bleaching" out the surface and making it a lot lighter than the head board.