The answer to your questions about the manual(s) and is it accurate is yes. The actual scope is made by a company called Pintek in Taiwan , and they are / were widely sold by other companies who effectively badge engineered them and had manuals printed with their company names and logos on them. Would I buy one like you did for $80, well yes, I did that a couple of years ago but have since moved on from them onto other scopes with more bandwidth, but in reality, here is nothing wrong with 30Mhz bandwidth, certainly more than enough for a beginner and or audio work.
If you PM me with your email address then I can email you back all the information I have on this family of scopes including a service manual. I emailed the factory in Taiwan and asked if they had a service manual, and they very kindly emailed me back with one.