sliver of wood, etc.  One last thing; I thought it was less honorable to ask
someone to help one kill himself...  and if Ranma really really loved his
friends, he would do it himself.

No, it's not. Someone always had a 'second' who chopped the guy's head off
after he slits his stomach. This is so that he doesn't take forever to die.
Usually it would be the guy's mentor or someone close to him. In this case,
it was Ranma's mother, who would be doing that job, anyway (see in the
manga, she's the one with the sword, standing over them, while Ranma and
his dad kneel down with the small knife/dagger things at their stomachs?
That's because she's the one who would chop off their heads, to finish the
job.)

I thought the idea was that having a Second showed honor to the one
committing seppuku (whatever their reasons) by not forcing them suffer.  If
you were seen to be totally without honor you didn't get a Second and had to
suffer it out.

Yep... the second then usually killed themselves after their master or 
whoever it may be. But comitting seppuku meant keeping honour, anyway...
Anyone who commits seppuku, even if they didn't have a second, was keeping
honour. I think it was just the nobility/samurai/etc who had seconds..?

Kun-chan...