Do I need a crank puller?
Do I Need A Crank Puller? Yes, there are ways to remove cranks without the crank puller but they will almost certainly do a lot of damage. There is no reason not to buy a crank puller as they a fairly prices starting from $8.99 upwards.
Can I just replace crank arms?
Yes it is possible to just change the crank arms with out buying new chain rings and BB. You can use 105, Ultegra or Dura Ace. Just make sure you have the correct bolt circle diameter for your rings as there are three different types of cranksets on the market (doubles, triples and compacts).