The three guides in the heads consist of 2 long and 1 short - don't remember the length. Yes, there is slack enough to remove the cam sprocket, all you need to do is loosen the tensioner and the sprocket is held on by that one bolt, but does have a keyway. If rolling in a new chain, by all means do the tensioner too. The tensioner is held to the block by 2 14mm bolts, that's it no pins at the tensioner. Also, if you decide to roll in a chain, change out the upper guides first as the old chain will afford a bit more slack.
To reinstall the pins, I used one of the fan bolts (6x50), threaded it in till bottomed, then tapped on the bolt head until pin was seated.
Not sure at what point the lower guides need replacing, but yes they require removal of the timing cover.
'73 280SEL 4.5 (9/72)- RIP
Only 8,173 units built from 5/71 thru 11/72
'02 CLK320 Cabriolet - wifey's mid-life crisis
2012 VW Jetta Sportwagon TDI...at least its a diesel
Non illegitemae carborundum.