There are some used screens @ ebay. How about asking one of the local sellers what the steps are in replacement... . I can't imagine it being too complicated but i haven't worked on a J1 before.
I have worked with aftermarket screens and they are not as good as OEM as far as brightness, but if you don't care about that there are some good prices on the aftermarket screens. The only thing i would suggest is try to get one with the backlight already attached (ask before buying). Here is a recent search on [http://www.ebay.com/sch/Digital-Camera-Parts/64352/i.html?_from=R40&_nkw=nikon+j1+lcd|J1 LCD's on Ebay]. You will want to get the ones that have 2 flexes (1 for the backlite and one for the LCD)
You can always just remove the external screws (keeping note of your every step and where the screws go) and try to get the back off. Once the back is off you should have a better idea how accessible the LCD is.
Please be careful because cameras still hold some residual power and can get a good jolt (stay away from the flash area). Beware of Static Discharge and ground yourself properly and try not to work on a carpeted surface.