How are Buddhist Sacred Texts used in practice and historically, given the questioned authenticity of some of them I'm curious on how Buddhist Sacred Texts are used in teachings and in practice. 

The Buddha often says not to solely follow transmitted tradition, instead Buddhists are "exhorted to know for themselves." 
(Pg 2-3, of Scriptural Authority: A Buddhist Perspective by Shi Zhiru).
However, some sutras give sacred texts a much stronger authority (Pg 4). 

Given that some sacred texts are not evidently authentic, some of which are written hundreds or even thousands of years after the Buddha's passing, what authority do practicing monks and the Sangha give to the sacred texts? How are these texts used? Are they used merely as a guidebook or as intensely analyzed, as say, the Christian Bible?

I appreciate any answers with any sources if used! Thanks
From a more secular perspective the Pail Canon has the definite merit of being closer to the time of the Buddha so could (controversially?) be argued has the greatest authenticity. However there is an enormous canon of Mahayana literature that from a historic point of view was written hundreds of years after the time of the Historical Buddha. To the adherents of these forms of Buddhism these texts most certainly don't lack authenticity. In fact the ones that I'm familiar with go further and insist that they are higher teachings that build on more provisional early texts.

A couple of examples

The Perfection of Wisdom sutras are early Mahayana texts. The tradition goes that the Buddha entrusted the texts to the Nagas (water snakes or dragons). Hundreds of years later Nagarjuna rediscovered these from the nagas then redistributed them to the world. So according to tradition the texts are authentic although they were only available much later on.

Another Mahayana text the Lotus Sutra goes to great lengths to point out that the text is the authentic word of the Buddha even though it was written after his death. It asserts that it is a higher teaching that augments and to some extent supersedes the early texts. In this case the Buddha is still teaching the text but in this work the Buddha is seen more as existing throughout time and takes on a more cosmic aspect so the words been written afterwards become less of a problem. This quote illustrates the timeless aspect of the Buddha in the Lotus sutra


  Suppose all these worlds, whether or not a particle was left in them,
  were reduced to particles, and each particle represented a kalpa. The
  period of time since I became a buddha would exceed this by hundreds
  of thousands of myriads of koṭis of nayutas of incalculable kalpas.
  Since then I have constantly been residing in the sahā world,
  teaching the Dharma and inspiring sentient beings. I have also been
  leading and benefiting sentient beings in incalculable hundreds of
  thousands of myriads of koṭis of nayutas of other worlds.


Use of the texts

As to how people understand of use these texts - since the later texts are still seen as the authentic Buddhist text they will be used in that manner. Bear in mind also there are texts that do not make the claim to be the authentic word of the buddha such as Santideva's Bodhisattvacaryāvatāra. A huge number of people, past and present, find these texts hugely rewarding spiritual works in the same way as people have an enormous regard for Christian works such as An Imitation of Christ. It doesn't need to the the direct word of the the Buddha to be a valuable spiritual work.

I have personally read (a reasonable portion of) the Pali canon and the Mahayana works listed here (Diamond sutra and Heart sutra from the perfection of wisdom) and I would urge anyone who is interested to spend time with the Mahayana texts as well as the Pali Canon texts. It's my belief that these works aren't (just) instructional manuals - the reading of them is an act of devotion and Buddhist practice in and of itself. Read the Lotus Sutra and allow the great swirling cosmic vastness of it all transport you somewhere else.