Audio Editing

I need 2-3 audio files that are each only 2-5 minutes long to be edited. Specifically I require some parts of the audios to be removed and then SEAMLESSLY blended back into the audio file. If the quality of the audio is effected a little that won't be a problem the key thing is to ensure that the file is blended back in so that the file continues without being able to tell that its been edited.