question about synching ipod and itunes

I dont trust the auto sync on my itunes and would rather do it manually. this works fine except if i change things on old mp3s. for example lets say i add some cover art or i change a typo or something. then i have to remember to delete the old file on my ipod and move the new one on. if i turn on auto sync, will it update my ipod to look like my itunes playlist? in other words could i leave it on manual, but every once in a while if ive made some changes could i turn auto on to sync my pod up and then go back to manual?

also its very important that it updates the pod to look like the itunes cause i dont want to erase the changes ive made in itunes.... does this make sense? any help would be appreciated