Here's why:
1) Their equipment wouldn't "talk" to your ECU eh? Absolute rubbish - any EODBII reader will read codes from your engine, and come on, this is a Nissan garage, they should have enough diagnostic kit to make you drool, I have trouble believing this.
2) 82 Euro to do a full diagnostic? They're having a giraffe. What does a "full" diagnostic consist of? About the only thing you can do is to read the codes, clear them, see if they come back, and record some live data. The last bit is almost certainly not necessary, and the rest is a 10-minute job. You can do this with your own code reader, which you could buy for a lot less than 82 bucks. If you really don't want to get your own, then go to a decent independant mechanic, they will often do code reads for free, or at least for beer money.
3) Timing chain? They're happy to diagnose a 1,000 Euro job without reading the codes - sounds like they're heavily into your wallet here. Sure, at 191k it might be the timing chain, but until you see a code for a cam sensor fault you simply don't know.
Sure, all the things you mention doing are fine, but don't be surprised if they don't actually clear the fault - I still go back to my (and others) original statement - get the codes read. I hear you start talking about swapping the engine, yet you don't actually know what the fault is yet - madness IMHO (no offence!). The last place I'd go would be a Nissan dealer, find someone with a code reader or go to a decent indy would be my advice, you shouldn't be paying more than about 10-15 bucks for a code read, tops.
We have a primera too - I agree, a good car and good engines, well worth fiddling with. Ours was my aged father's from new, it's 10 years old and has only 25k on the clock!
All the best with it - keep us updated!
Cheers
