Perosnally i change it every service, i service it myself. If you do a search ull see people reccomending Redline oil, and id reccomend it too. Change it every service, the better lubed up your car is and the more u service it, the more its gonna last and perform better.
Drain it using the plug
Throw some redline lightweigh shockproof in it (you only need 2.5 litres
Seal up the plug
let sit for a while, then go for a drive going easy on it, to let the oil run over all components, take it home and your done