Yes, but 800-1000 years ago the language differences ought to have been smaller, as I believe both the Saami and the Finns originate from the same group migrating from the East (although I don't know when that happened. Apparently the group moved in to a population vacuum resulting from the previous Finnish population largely dying off before the migration [so the migrants do not appear to have been the cause]). Also, the "contamination" from Swedish ought to have been smaller at that time (I don't know whether the usage of Swedish along the coast resulted from contact, migration, or both, nor when Swedish got a foothold there), apart from it being independent of the political powers.
At the time of the UrW time line the Vikings appear to have had no major problems speaking to each other, while nowadays Icelandic is too far removed from the other languages to be understood without some training (or, rather, the case is the reverse, as Icelandic has changed little, which the other languages have changed a fair bit).