well... in full and long almost tutorial-like form
now i recommend u make 2 models for your character... i of his whole body missing an arm... and one of the arm weilding the sword. This is planning ahead for a problem u will undoubtebly encounter. more on that later.
Now you'll have to animate the arm separately from the body and still make sure it looks right

should be no problem. When in darkbasic, u cant just glue the arm to the limb because i dont think the animation will run... although it may be worth trying it 1st... i cant remember. but if not, at the beginning of every loop u'll have to position the arm at the eaxat position and angle of the center of the body... the move it in which ever directions necessary.. this will involve alot of experimentation.
Once you have the arm, looking like it is part of the body, you can add attack button. Now by having the arm separate, it means the attack animation wont distub the body animation... so when in mid-run your character wont suddenly stop, do the attack, then carry on running. If that is what you want then i recommend ignoring the above, and just having the whole body, sword and all as one big body.
For collision: You intend to rotate the arm with the sword glued to limb then use the check collision commands, or the position comparison. Neither of these work. When you glue to limb it completely fudges up everything about the glues object to do w#with position size etc... so... instead:
When you press the attack button, have the model move forward x units (depending on how far his could could reach), but dont update the screen... instead check collision... if not then have him move back to where he was and carry on as normal without hitting anything... but if there is collision, have him move back to where his sword would be touching the other persons sword... if there is still collision the opponent has aprried the attack... of not, then you have hit because you are close enough.
Will take alot of experimentation... and there is probably a better way... but im remaking prince of persia and thats how im doing it until i think of summit better
uk.geocities.com/maniacimagine check it out. ill soon be formally opening it.