Here ya go - again, in order, this time from the top down.
You're welcome. It's why we're here.
Your mechanic should be a little more helpful. Then again, their time is valuable.
That oil filter wrench is perfect IF the bottom (closed end) of the filter points down, or is pretty accessible. You'll need a 3/8" drive ratchet to loosen it:
http://www.harborfreight.com/38-in-driv ... 62287.html Righty-tighty, lefty-loosey.
Don't put the new filter on with the wrench - thread it on by hand, then hand-tighten to "snug"... no grunting.
Yep, SuperTech. It's just fine for your car. No need for synthetic. If it's always had conventional, stick with that. The shops buy their oil in bulk, so they don't even usually know what brand it is. Use the viscosity recommended in your manual. Absent that, 10w30 is a safe choice. Remember this: The BEST oil is CLEAN oil. Your Sentra won't know the difference - she's not running on the ragged edge of performance.
Same with the filter - Don't go crazy. Save your cash, get whatever is on sale. Some of the Fram filters have the grippy texture, which is great - you may not even need a tool to remove it (if you have moderately strong hands).
O-rings are incorporated in the filter - No need to buy.
There should be another dipstick (for the transmission fluid) towards the driver side. It should be somewhere under the airbox. In your pic above, start looking down about halfway between your oil dipstick and red battery terminal. As an added bonus, IF you follow the above directions and find it's low on trans fluid (I'll bet it is, so don't drive until you check it), you can top it off right through the same hole the dipstick fits into! Convenient, eh?
Here's the FSM (page 32) for your transmission fluid check:
http://www.nicoclub.com/service-manual? ... _Sentra/ma
Do NOT get under the car without jack stands. 3-ton are perfect (buy 2).
There's some great info in the Factory Service Manual, which I'll link you to here:
http://www.nicoclub.com/archives/use-ni ... abase.html
Your homework for the next 24 hours, if I may: Read through this entire section -
http://www.nicoclub.com/service-manual? ... _Sentra/ma