hi all i have an oil from behind vct unit on my au ute is it hard to fix also how do i know if vct is working

Take the bolt out that holds the upper idler pulley on then smear the shank with silicone. Re-insert & tighten. If leak doesn't stop, repeat with more silicone.

Not sure how you would check if the VCT is working on the fly.... someone elses turn for an answer