First, some of how Lyco suggests that the valve tappet assemblies should be handled is described here - http://www.lycoming.com/Portals/0/te...0Lifter....pdf

The procedure that you are interested in is mostly described here - http://11hc.44rf.com/manuals/engine-prop/lycoming/aerosportspower-library/360_series_ops_manual/sec_5-maintenance.pdf

How long will it take? If you budget a half hour per cylinder you are unlikely to be disappointed. Someone who has done it a few times can likely do it much faster, but I think that a half hour is a safe guess.

Best of luck,

Wes
N78PS