WordPress Plugin Development

We need a freelancer to remove the ReachShip plugin and add the ShipStation plugin on my existing WordPress website. I have a test environment. I need to be sure that the sales tax calculation will still work with the plugin (something I am struggling with now). I also would like to change the order of some items on the checkout screen. Currently the "Direct Deposit" is showing before the Credit Card payment option and we believe this is confusing customers. I have the same issue with the Shipping Option. The in-store pickup is showing first and customer's are selecting that option, even though they are not able to come in, and would prefer we ship. I would like to discuss any coding that needs to happen to make these changes. In other words, if the module cannot do this on it's own I'd like to know about it first, before you make custom code changes. I have run into issues with my website not functioning after a module updates and the custom code breaks the website.