Clarify update for .NET instrumentation

internal/buildscripts/packaging/installer/install.ps1

@@ -69,7 +69,8 @@
     .EXAMPLE
     .\install.ps1 -access_token "ACCESSTOKEN" -with_fluentd $true
 .PARAMETER with_dotnet_instrumentation
-    (OPTIONAL) Whether to install and configure .NET tracing to forward .NET application traces to the local collector (default: $false)
+    (OPTIONAL) Whether to install and configure the Splunk Distribution of OpenTelemetry .NET to forward .NET application telemetry to the local collector (default: $false).
+    If the instrumentation is already installed the script will update it to the latest version - stop all instrumented applications before attempting to update the instrumentation.
     .EXAMPLE
     .\install.ps1 -access_token "ACCESSTOKEN" -with_dotnet_instrumentation $true
 .PARAMETER deployment_env
@@ -703,7 +704,14 @@ if ($with_dotnet_instrumentation) {
     if (-not $currentInstallVersion) {
         Install-OpenTelemetryCore
     } else {
-        Update-OpenTelemetryCore
+        Write-Warning "Splunk Distribution of OpenTelemetry .NET is already installed. Updating to the latest version..."
+        try {
+            Update-OpenTelemetryCore
+        }
+        catch {
+            Write-Error "Failed to update Splunk Distribution of OpenTelemetry .NET. Stop all instrumented applications and then try again."
+            throw $_
+        }
     }
 
     $installed_version = Get-OpenTelemetryInstallVersion