heres the thing. Its your toy. who cares what you do to it. Unless you are worried about OPO?
many people take a rare toy and putz around with it. Many people will feel its not right, but there are those that feel, if its mine, i can do what i want.
IF you want to sell it later, you can. But consider if you want to putz with it and you want to get the most money out of it, then you may want to sell it now and get a used or newer gun to putz with. If the quality of your work is top notch then some wont care what you do, but some people walk on water in their own minds too. you state you have made that mistake before. I would hope you learned from it?
If you are going to do have a competent gunsmith work on it, then you should be fine. Just a note even a competent gunsmith and screw up too. its happened. But one other thing to consider is that if all you are going to do is to swap out sights, then i would keep the OEM and when you decide to sell that gun, just put it in the box so the new owner can decide if they want it OEM its available to swap back. But if you start to make physicall mods where its not OEM, then dont expect to get top $$$ for it. I go by if it can be put back as OTS, then its not a big deal to me what mods were done. But once you start going beyond that, then to me and how i collect guns, its lost its value.