I used to live in Sault Ste. Marie -- the salt ate my K-car in about three years!
Sorry to tell you that there are no replacement bushings for the rear suspension, the links must be replaced. They aren't horribly expensive, but this isn't really a DIY project if you don't have jack stands and a hydraulic floor jack -- not safe.
Your front end squeak could be the upper pivots on the suspension (a variation on McPherson struts, I think) -- they go bad and creak. Have your ball joints checked for wear, and check the rubber boots on them for damage -- it's fairly easy to get salt inside the grease boot, and it will eat the ball joints. Same goes for the tie rod ends (they turn the wheels, again fairly obvious). These will also squeak if there is salt in there.
And oil that car!!!! The only cars I saw up north that didn't get eaten up were oiled at least once a year!
If you cannot get to this shortly, try to find a decent independent MB mechanic to check things over so that you are sure you don't have a safety problem -- stuck steering or a broken ball joint isn't all that much fun!
1972 220D ?? miles
1988 300E 200,012
1987 300D Turbo killed 9/25/07, 275,000 miles
1985 Volvo 740 GLE Turobodiesel 218,000
1972 280 SE 4.5 165, 000 - It runs!