How do I change the pattern of a shirt and keep it natural?

[pansy_4786]

 I want to replace the plaid of the shirt (photo) for a different plaid (Buffalo check). Is it possible to do so without losing the details like butons,  lines/folds of the shirt? 

[c.pfaffenbichler]

So far you would still need to isolate the »plain shirt« and then insert the new Pattern (as several Smart Object instances to allow for separate transformations/Filtering for the various elements like pockests, sleeves, …). 

Ideally one should start with a plain medium-colored Shirt if one wants to insert other prints/patterns. 

[pansy_4786]

Thanks @c.pfaffenbichler for your suggestions. I tried to tone down the existent pattern and then applied the new one but it does not matter what I try, it always looks weird as parts of the base pattern shows through the new one. I dont have the option to work with a plain medium-colored base.. unfortnately. 

[c.pfaffenbichler]

Then painting it is, I guess. 

Creating a plain shirt with Generative Fill wil probably change too many relevant details to be useful.