Here are the commands for your Powershell script to remove and re-add a solution package in SharePoint 2010
To Open the Windows PowerShell Session :
1. On the Start menu, click All Programs.
2. Click Microsoft SharePoint 2010 Products.
3. Click SharePoint 2010 Management Shell
Note : You should have SharePoint_Shell_Access role on the configuration database and you should be a member of the WSS_ADMIN_WPG local group on the computer where SharePoint Server 2010 is installed.
Now, type in the following comamnds ( Note that the first two are needed only if the Solution already exists and you need to retract it before adding a new one.
Uninstall-SPSolution -identity {name of wsp file} -allwebapplications
remove-spsolution -identity {name of wsp file} -force
add-spsolution -literalpath C:\{FULL file system location\name of wsp file}
install-spsolution -identity {name of wsp file} -webapplication http://{URL of SharePoint site to deploy to} -GACDeployment -force
For more commands see SharePoint 2010 Windows PowerShell Commands - I