Around the year 1000, the vikings sailed and settled in Greenland.

/kloc-Viking navigation and settlement around 0/000 (theme)

The first modifier has no lasting effect on Greenland and North America (the second modifier). (predicate)

The sentence looks good after being dismembered by grammar.

The example of 1 is a whole with "those of the vikings", followed by "such as" as the subject, which can be translated into the meaning of navigators and immigrants among the vikings, meaning such people among the vikings. Of course, it makes sense to use vikings directly here, but this expression is more accurate because vikings are not all sailors and immigrants.

2. Yes.

3. The revised target is sailors and immigrants to Greenland and North America. The whole translated sentence is that the navigators and immigrants who went to Greenland and North America around 1000 AD, such as the vikings, did not have a lasting impact. The complete meaning should be combined with the context. If the modification has no lasting influence on Greenland and North America, it must be placed after impact, because have impact to sth is a relatively fixed phrase with no preposition usage. If the vikings began to sail and settle around 1000, there would be no late influence on Greenland and North America. Sailors and immigrants around 1000, such as the vikings, did not have a lasting influence on Greenland and North America.