I am going to make a corporate video on how to disassemble and reassemble the guts of a hardware unit we have on the floor at work. The part I will disassemble and reassemble, will be taken home so I can shoot the video at home in a quite room. I am wondering what you think would be my best option for audio would be. I do own a shot gun mic, any other suggestions? The video will be shot pretty close up so the small parts I am working with can be seen real close. Do you think it would be better to shoot the video then go back and narrate later seperatley. The camera will be focused mainly at the part I am working on, so you really won't see my lips moving. Thanks

One vote for separate narration. Cut the video and add narration.

If I am outvoted, you could use a lav.

I generally practice the job, write it all out, and narrate afterward.

Trying to talk and work at the same time is pretty tough. I do a lot of this kind of work. People have said that reading it sounds like you are reading, but with practice, I find I can read it with a lot more inflection than I can muster while trying to do the job.

I do sort of narrate the first time to help me write the script.

Thanks I appreciate feedback

Yes - I agree - narrate afterwards.

I might wear a lav anyway and record a guide track - could be useful for editing later.

All the best

Unfortunatley I do not own a lav or wireless mic setup. I can't see spending $400+ for a wireless setup of this kind for a one time project.

Practicing while recording a guide track is a very good idea. It will let you know the spots where either voice or action take longer than the other.
Depending on how good your concentration is you could play this guide track back during your actual video take. If you want clean natural sound of the video closeup, you could listen with closed-back headphones during the actual video take. Then do the final narration after cutting the video. Be sure to record a lot of ambient "silence", since you may have gaps in the narration where the action takes additional time.

Unfortunatley I do not own a lav or wireless mic setup. I can't see spending $400+ for a wireless setup of this kind for a one time project.

Consider rental as an option.