02' Lancer OZ Rally Problem

Hi I drive a 2002 Lancer OZ Rally and recently i feel something wrong with the transmission...its an automatic tranny, when it shifts gears it jerks..but it only jerks when its going from gear 2 to 3 (around 20-30 mph)... and also recently my "Service Engine Soon" light started to appear... im thinking i need to get a tune-up like doing an oil change, tranny fluid change, changing spark plugs, and changing air filter... I'm wondering if I do all this should would it stop the car from jerking and the service light might go away or should i have it checked up at a shop...any advice would be helpful..thanks in advance

have you tried a computer analysis of your engine. you might just need to adjust the valve timing.