After selecting the vertex you want to move onto some other, press "v", to enable vert./CV snapping.
Then simply "drag&snap" the selected vert onto some other.
Finally, yes, re-select & merge verts.
ps: a much faster way to do that is to download and install the Bonus Tools
. Inside this tools package, jut use the Poly Vertex Merge. Much faster. Click the vertexToMove, click the target. Done.