How to replace facia boards?
shirlock homes is correct.  The facia boards should be underneath the drip edge and it will not be affected.  I would go slow removing the facia boards in case the roofer inadvertently nailed the drip edge to the facia.  The steps are simple:


Remove facia using a cats paw or similar tool and a hammer.
Remove all nails and/or screws that might get in the way of new facia.
Replace any of the facia boards behind it that need replaced making sure to end each board on a rafter or truss.
Cut facia and nail it up with galvanized nails, (usually 2 every 16"-20") pushing up gently on the shingles and drip edge to move them out of the way.  If you have any angled pieces then a speed square is a must.  How to use one would require a whole nother question and answers.
Put a dab of caulk on every nail head and every seam on the facia.
Paint.