I will be arriving at Munich int'l airport around 5 AM
I want to get to the Munich Central Train station by the S-Bahn.
How far is it from the airport?
Do i have to change trains?
How much is the Fare ?
Thanks

How far is it from the airport?
~ 40 km
~ 45 min
Do i have to change trains?
No.
How much is the Fare ?
EUR 8,80. Day ticket is however only EUR 10,00. Thus mostlikely the better deal in your case.

this DAYticket allows UNlimited use of all buses/trams/metro/Sbahn in the greater Munchen area all day.
In case you ask this as you want to travel further onward by train: its ALL DB and a ticket all-the-way can be bought at Munchen airport station. That time=so early, only from machines (cash or cred.card)