1. You can do the replace when you select data from your data source by writing replace sql in your select statement. but in oledb replace function not available, so you may need to implement replace using InStr() and Len() functions.
2. You can change the dataset or datatable column values by using simple for loop and change the values using
string replace[
^]. then bind the updated datatable to your gridview
3. you can use RowDataBound Event of your GridView and change set the cell value after replacing. check
this [
^] answer and modify according to your needs.
I haven't provide direct answer to your question, you need to try your self and find your own solution. in case of issue you better ask question with what you have tried and where you stuck. good luck!