As i checked in the data, i didnt see any direct character save as you could find in the Diablo 2 files so i assume it isnt possible to just transfer one piece of data.
If you continue the game... then reload it to a previous point... does it feel very rewarding for you?
Then, for dinging someone willing to spend some time on the game, it isnt always easy to find some random dude since you could almost consider it as a commitement x)
No, I am afraid you cannot import your own character into the game. This is because of the game design: no level scaling, no respawns and a continuous character progression. So, it would be kind of impossible for your friend to save his character at level 3 and then import it back into your game when you have already reached level 10 after playing it solo for quite a while and there are only level 10 monsters left around.
