I helped with three M62 overhauls. One of the helpers that's done it before says it adds 6 hours. Valve seals would be more improvement engine out vs chain guides which I didn't find difficult engine in. The most difficult part is probably just getting the exhaust headers back on during reassembling. If you are doing chain guides you'll already have 90% of the hoses and wiring disconnected so it's not a big leap to pull the engine

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2011 E70 • N55 (me)
2012 E70 • N63 (wife)