The market/pricing of Merckx frames is quite variable. In the US the frames generally fetch more than in the UK/ Europe.
Merckx frames commonly appear on both E bay and LFGSS, so that can give you an insight.
My (short story version) experience is of having enjoyed riding a Merckx Corsa Extra (in Weinmann team colours - pink/blue etc) so much I decided to have it resprayed in red, with the various decals etc. I had this done at Mercian at a cost around £190. I couldn't then bring myself to ride this pristine frame, so I had it built up, unridden for two years when I decided to sell. Sold on the bay for £275, in pristine condition (frame and forks only). I'm confident if I'd sold in orignal condition I would have got considerably more than the £85 difference.
I've seen sales of pretty average condition ones go for late £100's (eg £180), albeit with original paint and decals etc. Others were asking £400 or so, but being available for a long time (despite various opinions expressed that the price is 'reasonable').
I don't think you will get your money back for the cost of a respray - better to allow a buyer to factor that cost in and they can get the coliur scheme of their choice. The lack of Merckx decals may reduce the market a little. Not sure what I'd do, but I would at least consider getting a set (eg Cyclemondo) of decals to dress the frame up, for the sake of £20 ish.
Pricing is tricky (there is a topic specifically for help on that on this forum), in the current state (no frame tubing sticker, or Merckx decals) I'd have thought around £100, maybe a little more. As I said at the start, the pricing is very variable - depends if you advertise when there are a couple of guys looking for a 59 you may do well, if not, then you could have a bit of a wait.
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