My newly purchased home has windows with plaster returns and marble sills, the problem is that I like traditional trimmed windows. I know the best way to acheive what I want is to rip out the sills, put in jam extensions and trim out from there but these windows have wooden blinds that are going to cost $1500 to replace and I like the durability of the marble sills. Does anyone have experience with just using the plaster return as the jam and adding trim with a 3/16" reveal, all painted white. Also, any suggestions on how to trim around the current sill that only extends about an inch would be greatly appreciated.

Thanks for your time.