If it was fine before and feels fine now, I would just ride it. If something needs to be adjusted, then you can get it adjusted piecemeal. (Ex: it's not shifting right at the back, get that fixed... or learn to do it yourself - I never ask for a "full tune-up" because it costs a lot more than what actually needs to be done.)

It most likely needs air in the tires and perhaps a bit of oil on the chain...