It could be a complete sentence, but in this case it isn't. The full sentence is:
།དེ་ལ་འཁོར་བ་ཞེས་བྱ་བ་ནི་རང་བཞིན་སྟོང་པ་ཉིད་ཡིན། རྣམ་པ་འཁྲུལ་པ་ཡིན། མཚན་ཉིད་སྡུག་བསྔལ་དུ་ཤར་བ་ཡིན་ནོ།
literal: Amongst these [two divisions, samsara & nirvana, mentioned in the preceding sentence], as for what is called "samsara": [its] nature is emptiness, [its] mode of appearance is confused, [its] characteristic is manifested as suffering.
freer: Of these two, "samsara" has emptiness as its nature, confusion as its mode of appearance, and suffering as its characteristic.
Note that this isn't the 1st sentence of the text, you missed the opening verse & a line of prose. A unicode text file and pdf of the complete text is available here:http://www.dharmadownload.net/pages/eng ... s_0028.htm
As you can see, this sentence is considerably easier than the one about Sachen receiving the Zhenpa Zhidrel. With Khenpo Konchog Gyaltsen and Günther's translations (Khenpo's translation is better for the meaning, but Günther, despite his bizarre terminology, tends to stick closer to Tibetan syntax), dictionaries, and some patience, a beginner should be able to figure out almost everything in the Thargyen independently.