Try downloading a copy of the service manual .
I don't know about the 1n , but on some cameras the position of the AF module can be adjusted by three screws on the base plate hidden by a sticker .
Obviously it will effect all lenses the same way , so as long as all your lenses are back focussing , that won't be a problem .
If your camera can be adjusted this way , be sure to be methodical .
Put masking tape on the base plate and mark the start point if each screw so you can reset to where you started if things don't work out .
Likewise , each screw should be turned exactly the same , otherwise will be different on one side of the frame than the other .
On some Nikon cameras their is a lobed cam in the mirror box you adjust The position of the mirror until what you see in the viewfinder matches up with the AF unit and resulting picture .
Though I'm not sure if this was just their early DSLRs or film cameras as well , and I don't think Canon did it this way anyway .
Just a couple if things for you too look further into before you attempt anything yourself .
Would an independent service centre not calibrate your camera to your lens ?
As long as your. Lear you don't want any adjustment done to your lens , it would effect the focus on the DSLR .
If all lenses are consistently off , you would probably only need to send it off with one lens to get to go us correctly .
The cameras I've adjusted myself are DSLRs I've converted for myself and others to infrared , and these have all been adjusted like this fine .
I couldn't say if the type of AF units in yours was the same as were carried over from film cameras to digital , but someone here that services cameras should know .
Also , adjustments made by the hardware method is less precise than adjustments made via software . But at least it's a DIY method .