Sample install.ps1 for a NuGet package that patches the umbracoSettings config file

install.ps1

param($rootPath, $toolsPath, $package, $project)

if ($project) {
    $projectDestinationPath = Split-Path $project.FullName -Parent

    ### Change single element value or attribute ###
    $umbracoConfigFile = Join-Path $projectDestinationPath "Config\umbracoSettings.config"
    $umbracoConfig = [XML](Get-Content $umbracoConfigFile) 

	# Set domain prefixes to true
 	$umbracoConfig.settings.requestHandler.useDomainPrefixes = $true
		
    $umbracoConfig.Save($umbracoConfigFile)
    
    ### Insert chunck of XML ###
    $dashboardConfigFile = Join-Path $projectDestinationPath "Config\Dashboard.config"
    $dashboardConfig = [XML](Get-Content $dashboardConfigFile) 
    
 	# Add new section to dashboard
 	$mySection = [xml]@'
    	    <section alias="liveLogger">
	        <areas>
	            <area>developer</area>
	        </areas>
	        <tab caption="Live Logger">
	            <control>/App_Plugins/LiveLogger/usercontrols/ViewLogs.ascx</control>
	        </tab>
	    </section>
    '@
	$mySection.PreserveWhitespace = $true
	
	$n = $dashboardConfig.ImportNode($mySection.DocumentElement, $true)
	$dashboardConfig.dashBoard.AppendChild($n)
 	
    $dashboardConfig.Save($dashboardConfigFile)
 	
    ### Change element with specific attribute value ###
    $webConfigFile = Join-Path $projectDestinationPath "Web.config"
    $webConfig = [XML](Get-Content $webConfigFile) 
    
 	# Change connection string
 	$connectionStringElement = $webConfig.connectionStrings.add | Where { $_.name -eq "umbracoDbDSN" }
 	$connectionStringElement.connectionString = "Datasource=|DataDirectory|Umbraco.sdf"
 	$connectionStringElement.providerName = "System.Data.SqlServerCe.4.0"
 	
    $webConfig.Save($webConfigFile)
}