Is it worth checking vacuum lines?

[ktlimq]

I have random hard upshift: 1->2, 2->3, into D. Sometimes it shifts smooth, sometimes it shifts hard with shake and bang.
A mechanic said that that hard shift was acceptable on old car, but I sometimes have harder shift than the hard shifts I had while I was test driving with him.

Vacuum modulator was recently checked. It holds vacuum, and was adjusted a little. Modulator dustcap was also replaced.
Then am I done with vacuum stuff?

Or is it worth checking vacuum lines in accordance with the vacuum routing diagram, and check whether there is crack on connection?

Is there the vacuum routing diagram available online or on MB service CD? I could not find one at alldatadiy or MB service CD.