How broken is the shutter? When I bought my 4x5 monorail it came including a 210 symmar in a linhof(I seem to recall - it is not at close hand) shutter that was 'broken' (former owners term, not mine.)
I removed the front plate to see what wasn't working , since it was broken already. The main spring had stretched the hook at one end that is supposed to loop over a post to allow it to be tensioned. Consequently it had fallen off of the tensioning post.
I extracted the spring, and cut off the strecthed end bit, and bent the next turn of the spring over to allow it to go over the tensioning post. Getting the spring back in took a few minutes. Then assemble, and bang, shutter was workable again. The high speed may now be say 2% faster due to an incrementally shorter spring, under a bit more tenson, but that is not a problem for the way I use the camera.
So don't be afraid to peek; if it is broken, it might be fixable.