We are going to need to know where the source of the leak is to help you with that question.
cracked hoses
Because there is a hole in the hose! Replace the hose
you have a vacumn leak.
water leak or bad thermostat
The simple and really only answer I can give you is to find the leak and repair it.
It's probably your Alternator that is going bad. That is if the battery and brake lights came on at the same time.
depends on where the oil leak is at
replace fuel cap with Nissan only OEM replacement.
replace the hose or gasket the is leaking, you can spray carb cleaner around the eng whil runnig to locate the leak the eng will try to stall
the valve cover gasket is bad, or the valve cover is loose
It will more than likely leak not make a funny noise. They have a releif for pressure when they go bad.
No, but do check at some reputable smaller garages; that seems high.