If you already have 2 layers, in most municipalities, you can't put another layer of 'anything' on top. The weight may crush the roof structure. Also, roofing nails won't hold too well.
You say your house is 1600 sq. ft.. Is that the living space or the total roof area? If it's not the roof area, you need to measure that. A shake roof that size would take a pro over a week to rip up and install. That's baring no rain and no other 'problems' under the existing roof. No, it's not that hard but it takes some know-how. You may want to work it out with the contractor that you'll do the demolition (to save some $$$.) Get an estimate for the demolition that's SEPARATE from the material and install of the shake roof.
This type of roof may or may not help the property value. If this type of roof is in-character with the house, and more so with the neighborhood, then the answer is yes. For example, a shake roof on a Cape Cod house on Cape Cod will maintain, or even improve, the value of the home. You may want to talk to a couple of realtors and/or home appraisers. As far as being the 1st one on the block to install such a roof, I'd check into the aforementioned. (I'd suspect your home insurer wouldn't be too happy because of the increased fire hazard.)
If you'd like more info from a 'biased source', try The Cedar Bureau with the same questions. My best to ya and hope this helps.