SFO to Pleasanton by BART.....Could you help me please???

Ok i'm thinking about give a "Surprice Visit" to somenone in Pleasanton and need yoour help because i will be using public transportation to go there...
I would like to know what i have to do to ride the BART when arrive myself to SFO.
Which platform do i have to wait?
Which train do i have to take?
What kind of ticket do i have to buy?? ( I will arrive in a morning flight and return in a evenigh one, so it's a round trip flight)
I think i will arrive around 9am to SFO and leave at 630pm

Helppp me!!!
ALL ADVICES AND SUGGESTIONS WILL BE WELCOME!

P.S. I want to know if my heart is still in the Bay Area! i'm not ok and the solution is this trip.....

The SFO station is located at the International Terminal (Concourse G). From domestic, you can either walk or take the AirTrain. Once you reach the BART station, buy a ticket worth $15.30 from one of the machines. That will cover a round-trip from the airport to Pleasanton.

- If you're arriving on a weekday, there are no direct trains to Dublin / Pleasanton. So, you'll have to transfer at Balboa Park.

- If you're arriving during the weekend (or at night), there are direct trains to Dublin / Pleasanton from the airport.

you are looking at a long BART rise that will consist of Transfers. I would check out the website for BART it will help you plan your trip and give you all the info about riding. It is going to cost you about $8.00 one way $16.00 roundtrip. I have planned your outbound trip with the link below.

BART is very easy to use. you take an airport shuttle to the bart station at the airport and from there you catch a train.
you're looking for a dublin-pleasanton train.
you buy a ticket at the station, the price depends on the distance you are traveling.

it's very easy and bart employees or random strangers will help you.