check engine light, what's next?

[c280rookie]

hi guys.
i am new to this forum, but have been posting at other forums.
i have searched in other forums and posted my problems.
i am posting here to get more feedbacks and advices.
my check engine light came on yesterday. then the car suddenly felt sluggish and seemed hestitating on acceleration. i would like to know what could be the problem, as i have replaced my maf and ovp about a month ago.
i have been reading in other forums that oxygen sensors may need replacing too.
also, i may have to get my own obd scan tool. any particular brand i should get? i want the most user friendly available and possibly the cheapest.
thanks for you help.