Before looking to adjust anything look to find what has failed, you'll save yourself some time later.
There are no trimpots to adjust pincussion in your monitor, it is software controlled, so the only way it needs readjusting is after a repair or if the EEPROM has failed, but in that case you'd have other symptoms.
Look at the second link Rasz posted for the SIIA chassis it should be close enough although component positions (numbering) may not be the same, your chassis is SII.
Check solders in the H deflection, beware of split blue ceramic disc caps.
Check that glue has not come off inductors letting the ferrite slug loose.
Check the equivalents on your model of: Q551, C553, R561, L551, C506, C501, C502, D501, D502.
Also worth checking while you are in there: C509, C514.