replacing old rivet leeper hangers?

i hope to update a route with new bolts. can the old leeper hangers,rivets just get yanked with a bar? should i use the old hole or make a new one? is it practical to upsize the old hole with a hand drill? have drilled a ton by hand but never tried to upsize an existing hole..does anyone know whos rope is on the steep side of the 235' cliff off beaverbrook canyon road..... .4 camalot and a bolt at the top,blue rope. man i have been eying that wall up for years and would love to help out with the new lines as well as the old ones that need updating.

Some good resources here:

safeclimbing.org/education.htm

vimeo.com/53299008

A search of the forums here should also yield some tips for the use of tuning forks. Sometimes you can buy the forks from Greg Barnes at the ASCA. You can find him on this site.

cool. just what i was looking for.....very helpful.