A slight inconvenience in TOYOTA Caldina AZT241W

My lovely TOYOTA Caldina AZT241W has a problem to tremble at only idling situation. This phenomenon is not so apparent but very slight and it happens not always but once or twice a day.
Judging from the Website information, D4 motor with direct injection construction had a critical problem to pile up much sludge in the intake manifold because of it's innate injection pattern. And the inconvenience was taken measures as a style of manufacturer's recall, my vehicle is inspected and taken measure already, the record paper remains.
17 years old and 150,000 km used vehicle has many parts to be replaced now if I desire to continue comfortably, under such an unfavorable condition, replaced all the motor and trans-axle mounting parts with genuine ones by myself.
Also, disassembled I the alternator and starter for confirming the conditions of breakable parts such as blushes, magnet switch and supporting main bearings. All the ball bearings were re-greased from the inner space of sealing including the serpentine belt pensioner and air conditioner compressor. Thanks to this complicated work, high frequency disturbing noise from the bonnet inside disappeared.
In order to have some preliminary knowledge for intake manifold disassembling, opened I the bonnet of her and my motivation to proceed was destroyed at all after recognizing the layout of the cylinder head construction, front exhaust and rear intake. The way to the destination for accessing is limited within 10 cm only, how come!  It means more difficult to work on intake manifold or it might be impossible without unburdening motor and trans-axle heavy mass thoroughly!
Is it worth doing with putting on such a complicated and sweaty works on an old vehicle?