I replaced the wall light switch for ceiling lights and the receptical with it. Both are in the same wall metal box. Now when I put a plug in and then take it out of the receptical, it causes the light in the adjoining room to go off briefly. How should it be wired to avoid this?

Just found out that the house we purchased need new wiring in the kitchen. The electrician could not find where anything was coming from or going to. I have the knowledge on how to do this and usually do it before putting up walls. The kitchen is in good shape besides the electric. Here is my questions, is there some tool I can use to snake the wire to a light in the center of the kitchen ceiling and through the walls? I am going to be pulling old wire if poosible and adding a new breaker. Any other advice would be greatly appricated. Thank you in advance for your help.