I second that.. just replace it. the replacement radiators (atleast the ones the dealer sells) have metal reinforcement in the neck. Replacing it isnt such a difficult job if you like to do it yourself. There used to be a post for the W124 replacement under DIY section on this site but i just checked and link is not working. I would say it's no more than 2 hours worth of work if you want to take your sweet time and do it all yourself. probably lot less if you've done it before. Oh and while you're at it. what color was the coolant that leaked on the ground ? green or white ? If it was green then the previous owner used aftermarket coolant. stick with it. if it wasn't green then the original merced3es coolat is used. make sure you buy the bottle from the dealer before you open up the radiator. or if you take it to a shop make sure you give them the MB coolant and make a point to tell them NOT to use the green stuff. if you mix them it's not a pretty site.
good luck !
Whether you think you can or cannot, Either way you're right!. by Henry Ford.