The comment form of this blog was broken the last two days. The reason was that I disabled the no_cache parameter in the install tool. It seems the ve_guestbook extension somehow relies on this parameter. The comments are now working properly again. Sorry for the inconvenience.
The most accessible way to configure a plugin in TYPO3 is using a custom content element build with FlexForms. It provides forms of all kinds for any BE user. FlexForms adapt most of the features of the TCA, but unfortunately the documentation on FlexForms is rather poor. The following article tries to demonstrate the configuration of a TYPO3 FlexForm in order to get some forms which dynamically change their fields on user interaction.