Replace atmega8u2 with 16u2

Development Tools IDE 1.x
1

Is it possible to replace the atmega8u2 chip on a arduino r2 with atmega16u2?
i cannot upload any firmware to the atmega8u2 and arduino software cannot upload any sketches.

after i change the chip, which firmware do i have to upload to the atmega16u2, and wich board i select in arduino software for upload sketches to it?

2

The 16u2 gets:
hardware/arduino/firmwares/atmegaxxu2/Arduino-COMBINED-dfu-usbserial-atmega16u2-Uno-Rev3.hex

After the upgrade the Arduino UNO is still an Arduino UNO so you still select board Arduino UNO.

3

Got a hot air rework station? That's what's really needed to remove/replace the very little chip.