Fairly complex Audio/Video editing question

[Still in M0ti0n]

Here is my plan... I am going to create a video of me calling and ordering a pizza using a talkbox. Sounds pretty easy, but I want to do it so that the video has good sound quality from the talkbox and good quality audio of the person who I am talking to.

It would be easy enough to just film me talking to them through speaker phone, and the microphone on the video camera would pick up the sound from the talkbox and the other person's voice, but the sound quality of the talkbox and the sound quality of their voice would be terrible. So what I plan to do is plug a headphone splitter into my moblie phone's headset jack, then plug my phone heaset into one side of the splitter and a line out to my computer in the other side of the splitter. That's how I will get a clear sound recording of the entire phone call. (I saw a great tutorial on youtube on how to do this step of the process.)

The next step is to get a good quality recording of the sound from the talkbox, which I will hook up like normal. I will record it through a good quality studio microphone into an audio/video editing program on my computer.

Then I will load the video recording of me into the same editing program and mute the audio. Then I will match up the other two audio recordings with the video and mute the talkbox during the sections of the phone call recording when the talkbox on the good quality recording is playing (so that there is not a double sound of the talkbox playing on both recordings at once). This way the video will have the best quality sound from the talkbox and from the person's voice on the phone call.

It would be a lot easier if I could find a good iPhone app that records phone calls directly on my phone, and then I could just move the file from there into the editing program. All the phone call recording apps I tried were garbage though, does anybody know of a good one?

Any tips and tricks from people who are experienced with this sort of thing would be greatly appreciated. I am not very experienced with video recording and I have no experience with video/audio editing in tandem. Maybe there are some corners I could cut somewhere to make it all less complex without sacrificing quality. Thanks for the help!