Matching up will be easy. You'll need tile and halves not just a tile where missing . Its a winchester cut detail and it will be a T&H cut on the angle
Picture 1 lift the flashing carefully as it looks dodgy anyway., remove two tiles over the slipped one.
Reposition and fix the slipped one, while your at it put a nail or screw through any tile hole visible.
Re assemble and dress lead back flat.
picture 2 pretty common this one, options are strip down from the top Cut new tile , nail it on , put tiles back
or, Cut your new tile to required shape, Its very likely the top of the original will still be up under the tiles above.
try and get it out.. but may be hanging on a nail.
If its too tricky then make a hook from Stainless steel, pump a load of adhesive in there , bed the tile down , bend up hook.