Welcome to the forum, Summers!
Parts are still available and pretty easy to get. If you search the forum you'll find many threads discussing the subject. Most of the unique parts for Epic boats are around the engine such as: the engine computer, exhaust manifolds and the stainless steel head gaskets. Captain Rick has these parts in stock last time I checked, but contact him for pricing and availability. Per Wikipedia and Edmunds, the other parts for the engine are also available from Lexus (Toyota) for the 1998-2000 GS400 (300 hp), LS400 (290 hp) and SC400 (290 hp) that had the 4.0-litre automotive version (1UZ-FE) with VVT-i which is very similar to our marine engine (M1UZ). Kincaid Marine Rolco in Australia lists exhaust manifolds for a Lexus 4.0 LT V8.
Other parts on the boat are common, off the shelf parts that are used throughout the marine boat industry; Johnson Sea water pump, ZF Hurth marine transmission, Mercruiser gas filter, Rule bilge pump, Medallion gauges, etc.
Spend some time searching the forum. There's a lot of great information here and super people that are most helpful. Please post pictures if you can and keep us posted!