What is a oil flush. What do I need. And how do I do It. Sorry this is a first for me. Also how much does AMSOIL cost.

98.5 SVT Toreador #5550 4/7/98
PERFORMANCE:
Resinator removal/replaced w/high flow resinator;
OMP Strut Tower Brace;
Reactive recharge fliter;
AUDIO:
JL 10";
Alpine CD;
Altec Lancing speakers;
Altec Lancing electronic crossover;
Halfer 4 Chanel amp (mids and highs)
Harman/Kardon 2 Chanel (Sub)
DREAMS:
3.0 liter;
18" Racing Heart C5;
more audio