How to change request parameters before passing request to proxy.

Hi,

I am using Nginx to proxy request to some backend server.
For this, i am using proxy_pass module to redirect.
Config file:
location = /hello {
proxy_pass: abc.com
}

I want to execute the following workflow.
Request to nginx server --> change request parameters --> pass the request to abc.com --> change the response parameters --> send response back to client.

Is this possible with nginx ? Any help/pointers to this problem would be appreciated.