Material Change

[fathom parcel]

How do i smoothe out/change the gray material while preserving all the details like the little stitch on the right etc.

I want to change the material but i think i need to smooth out the gray texture first so it isn't grainy
Idk how to do that without messing up the lighting.
I masked the gray part and added black and white filter over it and then I made a new layer with a pattern i wanted to use as texture and selected a couple of different blending options but when i did that the underlying texture comes through.

[mighty basin]

THis is quite tricky because any attempts to smooth the texture will result in smoothhing out the light/shadows as well and it will show
However, there is a technique where you can separate texture for colour (You don't want to tech the colour there)
It's called "frequency separation"
https://photoshopcafe.com/tutorial/frequency-separation.htm