You are talking about a seriously involved job. Whilst the M104 is derived from the M103 there are some big differences, especially as it appears that you are talking about a 3.2 with HFM rather than the 3.0-24 which has KE-Jetronic like the M103. The M104 3.0-24 might be a better option. Easier still, sell the 300CE and buy an E320 coupe, 320CE or even a 300CE-24.
I also notice you are in Sydney. Are you a club member. If not, you should consider it. See:
107.023: 350SLC, 3-speed auto, icon gold, parchment MBtex (sold 2012 after 29 years ownership).
107.026: 500SLC, 4-speed auto, thistle green, green velour.
124.090: 300TE, 4-speed auto, arctic white, cream-beige MBtex.
201.028: 190E 2.3 Sportline, 5-speed manual, arctic white, blue leather.
201.028: 190E 2.3, 4-speed auto, blue-black, grey MBtex.
201.034: 190E 2.3-16, 5-speed manual, blue-black, black leather.