Assuming that this is a 117/116 engine, I've done quite a few of these. At their age, intake leaks are pretty common. You'll want to replace plenum seals, injector seals, injector holders, injector holder hoses, all the breather hoses under the intake, the air intake seal and maybe the injectors. The reason why your mechanic doesn't want to do it is as mentioned in a previous comment, this job can turn south. The intake bolts can be more than likely to break than not. The positive is, when I've done this job when the car has good compression, good working fuel and ignition components, it can run like a brand new car. Especially at idle.