If you're erecting exactly as original Artie rather than adapting it's pretty simple, I've done it a once and I've changed size for 2 others which with a bit of thought isn't too difficult either unless it's a complex roof you're changing. The biggest issue you'll come across is rusted fixing screws and you'll need patience to get the glass out without damage, after cleaning the d/g units assuming they're sound I'd recommend buying some aluminium tape and sealing along all edges which will stop any moisture ingress in case you disturb the seals taking during removal.
I erected about 60 new conservatories when in business and it's just like Lego. As GSP said above check the seals/gaskets and make sure you use silicone in the right places, take care especially with the roof extrusions and gaskets and you can buy eaves sealing foam tape which expands after fitting if you need it, and internal covering panels can be replaced with off the shelf PVC cover sections from any of the numerous plastics companies on most industrial estates, the ones that sell facia boards etc.
You'll need to thing about how you're going to flash the roof to the wall and what kind of base or slab you need to build on.