R – Automating MSI Build Process

The low cost solution is to switch to using ClickOnce, which you can automate using MSBuild. But if you still need to create a Windows Installer package, you will need to convert your project to WiX (pretty straight foward) and build that with your solution.

This will get you started: Automate Releases With MSBuild And Windows Installer XML

When taking on a project that has never had an automated build process, it is easier to take it in steps. Do not try to swallow to much at one time, otherwise it can feel overwhelming.

1. First get your code compiling with one step using an automated build program (i.e. nant/msbuild). I am not going to debate which one is better. Find one that feels comfortable to you and use it. Have the build scripts live with the project in source control.
2. Figure out how you want your automated build to be triggered. Whether it is hooking it up to CruiseControl or running a nightly build task using Scheduled Tasks. CruiseControl or TeamCity is probably the best choice for this, because they include a lot of tools you can use to make this step easier. CruiseControl is free and TeamCity is free to a point, where you might have to pay for it depending on how big the project is.
3. Ok, by this point you will be pretty comfortable with the tools. Now you are ready to add more tasks based on what you want to do for testing, deployment, and etc...

Hope this helps.