A lot of the fallout would depend on who assassinates him and how.
That said, Al Gore was pretty much an empty suit Democrat who just followed the party line and generally got nobody excited about. His wife, Tipper, it should be noted, was heavily involved in the 90s "Violent Music" Moral Panic, and as First Lady would probably escalate that as a major issue.
Also, seriously, "Republicans plotting to undermine Gore administration"? Could you be a bit less openly biased? What else donyou expect a Republican controlled Legislative branch to do to a Democratic President? Kiss his ass and give him whatever he wants? Of course they're going to oppose Gore's politics, they're the oppositional party.