Vue Esp imports many 3d file formats, but not Daz Studio format, so you should export your figures from Daz in a format Vue can read ( I've heard obj is best for D/S import, but there are a few things that have to be done to get a good import with pose and textures)
Vue reads the pz3 (Poser) file format natively, so you may want to think about reinstalling Poser.
Vue Esprit is a paid for program, so it can't do less than Pioneer, of course in Esprit you have all the material editors available (basic, advanced, and function editor)
Finally, Vue7 should read Vue4 materials, but to be honest, the new Vue7 mats are so much more superior in terms of visual quality than any Vue4 mat., and any Vue4 plant.
If it doesn't, it means that the Vue4 material/plant is actually a Vue3 mat/plant, that Vue4 had no problem reading, but Vue7 won't read it at all, so you'll need to use the "old scene converter" utility on them, and this utility app is located in the "Tools' folder of the download or application CD.