I hate to disagree with Phil or David, but I don't think you will have any problem with the partial kit you describe. I also don't think there are *any* size differences in the bushings. The Sportline springs lower the car an inch or so, that's it. Otherwise, the suspension differences are as follows for the Sportline items vs. stock:
Sway bars - Sportline bars are thicker, front & rear
Control arm bushings (front only) - Firmer rubber compound
Rear subframe bushings - Firmer rubber compound
Springs - Shorter & firmer (higher spring rate)
Shocks & struts - firmer
That said, I have put Sportline bars & control arm bushings on 2 cars with over 200kmi. It made a significant difference. Both are lowered as with aftermarket springs. If you want a firmer ride but no loss in ground clearance, I think you should go for it. The bars are a bolt-on, and the shocks & struts can be installed w/o special tools. However, the front c/a bushings require a MB-specific spring compressor to remove the control arms, and the rear subframe bushings are NOT easy (and also require special tools.) Just a warning. I plan to buy the subframe tool and install the Sportline bushings eventually, just haven't had time yet.
More information than you ever wanted to know about sway bars for the 124 chassis are on this spreadsheet (requires MS Excel to open). It includes part numbers, dimensions, and prices. Note there is what I call a "Sportline Plus" option if you want even stiffer bars, but it will cost nearly double (~$225 for Sportline, but closer to $400 for the bigger bars, and a 2-3 week wait while they get shipped in from Germany):
http://www.meimann.com/images/mercedes/W124_stuff/MB_124_swaybars.xls
Here's a great deal on the regular Sportline sway bars:
http://cgi.ebay.com/ws/eBayISAPI.dll?ViewItem&item=1858891887
Good luck,