My ailing '77 240D

hello fellas (and ladies where applicable),
this is my first post on this BB and i hope that my time here will be well spent and full of greasy, diesel smelling engine work. here is my predicament:
about 2 weeks ago, my 240k+ '77 240D decided it was time to enter the mercedes great beyond. yes, the compression was too low to even think about starting. i think it actually laughed at me when i kicked her over the morning of her demise. however, i have not given up on the poor lass. i am determined to rebuild! i have prior engine rebuilding experience and believe myself to be fully capable of the task. however, i would like to be completely sure about what i am doing before i dive in. my question is this:
what must be accomplished in order to ensure good compression upon completion of my rebuid? i've heard that these engines have cylinder sleves that can be replaced. should this be done? should i replace the pistons and rings as well? or just the rings? or, just the rings all together. please help.

thanks in advance,
william gum