ok let me summarize. If you can sacrifice your resource, yeah go do it yourself. However, if you have money and you time is essence, yeah hire an agent (the legal one)
I have seen a lot of FARANGs , who tryna do their 90-day report, go back to their home due to lacking of papers. Moreover, FARANGs go home with doubt due to the IO's language problem and hand sign does not make any sense clearly.