One thing you need to keep in mind is that the web and winforms are two very different beasts that cannot be (easily) combined.  With the advent of Silverlight the boundary is being diminished though you still will not be able to host a Winforms component directly (discounting the possibility of ActiveX controls, etc).

TX TextControl DOES have a Web component available as well and you would be able to utilize that in your DotNetNuke instance as a module if you wanted.  You should start with the Michael Washington tutorials about module development if this is a path you want to take.