Is there a mission editor for Red Alert

Fortunately, there is. It is quite complex, and does involve a bit of mucking around with files in your Red Alert directory, as well as learning a lot of things about how to use the editor. If you are interested in downloading the mission editor, links to the archive where it is available can be found on the "Links" page at http://www.srt.zoomshare.com/ - a very handy Zoomshare-created site, which also provides several other helpful links to websites.