i know you know this but it depends on what needs to be done and what you want to replace... and what you want to replace it with.
i had an old epiphone sheraton II, that was working, but i wanted to "rebuild" it. was gonna replace the pickups with alnicos, replace all the potentiometers and knobs, and basically redo all the wiring my way. then i was going to replace all the hardware because the gold finish had tarnished away and looked like trash. when i priced it all out, keeping in mind that i was going to do it myself so no labor costs, i think i quoted myself about $700... just for parts. so instead, i sold her for $250 (about $150 less than any others were going for on craigslist)... priced to sell, and i bought an epiphone les paul in limited silverburst for about $725 with hard case and cable. im happier now. but then again there was no sentimental value with the sheraton.