changing oil and cleaning carb

[Dirtytoes]

okay, so i just bought the following:

new filter: quantity: 1

oil bottle: quantity: 4

bike: ex500

so basically i drain the oil, change the filter, and pour the new oil in...right? they had this book at the place i went to and it said the ex500 needs 3.6 (qts or bottle of gallon), thats why i bought 4.

also, how much does it cost to clean the carb? the shope i went to said $380 which is insane but this mechanic guy that i know said around $50-$80....where can i get it that cheap?

oil description:
PRO HONDA, GN4, GENUINE 4-STROKE
MOTOCYCLE OIL SAE 10W-40 SJ

i was gonna get synthetic since i heard that was better....but the guys at the shop said that my ex500 didn't need it, and it was for the more sporty bikes (R6, gixxer 600 and up)

i just want to make sure i bought the right thing before i pour it in.

any suggestions will be appreciated.