MY FIRST Zed

ok so it should be fine that today at a red light it sat at like 10 to 15, it a low mile car so just dont want to mess things up. i just had an oil change and i know it leaks a little oil from the hose and from the oil pan gasket being bad... as long as i get those fixed then i should be alright? one more question, when should i change out the timing chain and guides, i heard it should be done after 100k? should i do it?

Hi I'm new to the z world. I just got a 2005 350z without doing much research into there problems... always been a dream car of mine.. but any way wend I cold start my car it's oil pressure is around 100 120 psi until it warms up then drops back to the middle... after driving about 15 to 20 min it drops close to like 30s... I'm sure this can't be normal