I did this on my 1750GTV, it wasn't too bad a job, but the hardest part was getting the crank pulley off, you can't quite get the pump off without taking the pulley of on a 1750 and I presume it will be the same for your Spider with the earlier engine.
The Nut on the end of the crank is very tight, and it needs torquing up tight afterwards. Putting enough Torque on is easy enough with a long Torque wrench, but stopping the engine turning is very tricky. It's no use putting it in gear or it will just move the car, even putting the handbrake on was no good, because it just flexed the transmission and tyres about. In the end i jammed an Allen key in the ring gear on the flywheel, but then got the key stuck!. It took a lot of rocking prizing and banging to get it out again, all the time running the risk of damaging the teeth. I'm not sure what other way there is of jamming the engine, a long spanner jammed in the UJ on the propshaft seemed like an idea, but it just kept twisting out. I totally destroyed the crank nut taking it off to, so you need to buy one and the clipped washer as I expect the same will occur on yours.
Apart from that it was fairly straightforward
