I have a esp8266... i want to change its firmware, but i dont have a usb to serial conveter... that is if you dont count my arduino nano, my question is if i upload new firmware to a esp8266 buy going trough the rx and tx will that effect my arduino boot loader or sketch... although I'd be fine with a arduino the runs lua I'd prefer to stick with c on the main proccesor.
An ESP8266 isn't an Arduino. You might be programming it with the Arduino IDE but it's still not an Arduino and it's not using any "Arduino Protocol."
Each different chip that you program with the IDE has its own programming method. There's a variety of programs behind the scenes such as AVRDUDE and BOSSAC that do the actual uploading. The boards definitions file within Arduino just knows which one of those to call when you press the "upload" button for your particular board.
Yes, I often find that a spare Arduino Nano, Micro or even Uno is useful as a USB-to-serial converter.
Jumper the Nano "reset" pin to GND, so that the AVR stays reset. Then you should be able to use the USB/Serial function without affecting the AVR.