Interesting project - my thinking would be that if you are preparing a 33 for hill climbing and you want a 16v engine, it might be more cost effective to buy a 16v 33
But, this is what this list is all about!
I would say as long as you can get a hold of a complete 16v engine with all the throttle bodies, loom, ecu, sensors etc you are pretty well good to go to drop it right in. It will mate to your existing gearbox. If you are getting your flywheel lightened, it would make sense to rebuild the engine and have this done so it is balance with the crank shaft and clutch assembly. Rebuilding a 16v engine doesn't have to be expensive - you won't need to replace pistons or rods if its been looked after.
The complexity will be wiring it in, but if you have all the bits just be thorough and take your time to connect everything up.
Good luck
~Benjamin