When somebody asks for managed hosting, I always question what exactly they don't understand about a VPS/Server. Is it hardening the server security-wise, configuring the OS? What exactly is it? There are plenty of management companies out there that work on an hourly basis. It will take 15-30 minutes to set up and harden a VPS initially. After that, there really isn't much to do. Even if you have to hire them for 30 minutes every 6 months, it's really not that bad.
There are also control panels that do a fairly good job of taking care of the mundane tasks. I know a lot of people don't like using control panels, as it adds to the server overhead, but for $5/mo. (yes...the price of a cup of coffee) you can get DirectAdmin. For the price of taking you and the wife to McDonald's, you can get cPanel. Or Webuzo is a great free control panel. All will take care of some of the security aspects of the server, will allow you to easily configure the OS stuff, and it makes doing things like setting up databases, email addresses, etc. an absolute breeze.
The forum software itself, you should know how to install, update, etc. That's part of the tasks of running a forum. People try to hire folks to update the forum software, and moderate their forums, etc. Why even have a forum if you aren't going to learn the basics? Most managed hosts aren't going to touch 3rd party scripts anyway. Some will, but most won't.
If you really do need a managed provider, Knownhost and WiredTree are very good.