I had this same choice a while back. After weighing the cost of a remanufactured Bosch (~$85), and the cost of parts plus time to rebuild..... I bought the remanufactured unit. Plus, the remanufactured unit has a guarrantee... DIY does not.

just my $.02

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William
76 240D (W115) - 550K miles
78 300D (W123) - 200K+ miles