The most time consuming part to remove will be everything on the dash, from the lower panels to the final upper dash pad. This alone, if you've never done one before, could take upwards of 3 hours...if you've never done it before. With experience it can all be removed in about one hour. The remaining interior, everything from the headliner down to the last scrap of carpet could take upwards of 3-4-5 hours, again, if you've never done this before. Most of the time is spent figuring out how something is attached and looking for that last and final screw that's still holding it to the car.
MOST IMPORTANTLY---Bag all the screws, bolts and nuts, mark the bags and keep them with their respective part. Also, if a screw or bolt is removed from an odd location be sure to mark that bolt independently. Tagging the bolt with a note such as "below/right heater core" will help with the frustration later of trying to figure out where that thing goes. NEVER assume and NEVER tell yourself, "Ok, I'll remember where this one went." You'll end up saying that so many times you'll forget them all.
Another tip that can come in handy is to numerically mark the parts as you take them off along with a brief note of their location (if it’s an unfamiliar item). First part removed is #1, second part removed is #2 and so on. When reassembling simply start with the highest number and work in reverse. This is particularly helpful in and around the dash area. There are a few small brackets that become removable when all the bolts and pieces are pulled. Not knowing where these go later or when to assemble them, “Now does that go on before the gauge cluster or after?”, will eliminate the possibility of having to do things twice.
Cleaning all the parts AND cleaning the interior sheet metal now exposed and showing dirt will take another 4-5 hours. Less if you’re not particular with bringing everything to a sparkling clean. Now’s the time to clean, so why skimp. I’ve probably spent a low estimate of 12 hours just cleaning parts, carpet, bare metal interior and fabric. Now’s the time to clean since everything is accessible.
Install will be much quicker. Give yourself at least another 4-5 hours to reinstall everything. The dash alone will go in quicker than the time it took to remove. This is where the bags of bolts and numerical markings are most helpful. But don’t rush, be absolutely certain you have reconnected every wiring harness which was pulled. You do NOT want to have to pull the dash simply because you overlooked that ECU harness hidden behind the ducting.
My ’86 MKII restore has been stripped to nothing but the heater core and major wiring looms, that includes R&R of the dash more than once. Marking the parts has definitely aided with identification of the parts piles.
I don't suffer from insanity. I enjoy every minute of it.