Do I need a Texis DBA (database administrator)?

Probably not. Administering a Texis database is simpler than administering other databases such as Oracle. Texis runs as an application on top of the operating system and does not usurp operating system functions. So backing up a Texis database, for example, can be accomplished simply by copying a directory (but see below regarding redundancy). Texis does have various administrative aspects and configuration options, but overseeing those usually is handled by the application developer(s).