I use a 140 cap on my W124, and I assume yours should be that as well.
MB OEM hoses are pricey, but on the flip side, they last nearly forever...so unless you have discovered any actual damage to the hoses, I would leave them alone.
I think someone posted a how-to on radiator replacement in the DIY section. It applies to the W124 series, but it should be similar to what you will encounter.
Note that the transmission cooler is also part of the radiator, so after you find the drain plug to purge the coolant, you will discover a metal line bolted near the area. When you disconnect that line, you will get a trickle of transmission fluid coming out, so don't let it drain into the same pan you are draining the coolant out...
2009 ML350 (84K) - Family vehicle
2001 CLK430 Cabriolet (71K) - Wife's car
2005 BMW 645CI (124K) - My daily driver
2012 Mustang V6 (60K) - Daughter's car