A person can be very well educated in some areas, and very intelligent, and still not know a lot about how research works. And without that knowledge, it is hard (impossible?) to assess the value of different pieces of research.

Even knowing how research works, unless you are a specialist in that area (this means years and years of doing it professionally, not hours and hours of reading online), you can't evaluate the research done. This is true in all scientific disciplines, not just autism research or vaccination research.

This is why it is so important for laypeople or even relative laypeople (ie specialists in related areas) to rely on the peer-review process. In other words: research that has been published in peer-reviewed journals of the highest rank (high impact factor), and that has been confirmed by many subsequent studies, can be trusted. Research that has not been so published and so confirmed is a lot harder to trust and sometimes is downright wrong. An example of the latter is the original piece of research linking MMR to autism that has since been retracted by most of its authors and disproven as thoroughly as possible in the years since it was published.