For all practical purposes you would not do anything to the gas block or front sight. Like already said, you can't use a bayonet anyway. Your rifle does use the short gas system of the AMD65 as already mentioned, which means the gas block had to be brought closer to the receiver. It would not be feasible to change that. The gun will work fine as it is.
I recommend you send it or take it somewhere professional for the barrel threading. It is possible to mess that job up. At the same time, it would be smart to install a muzzle attachment indexing spring and plunger in the sight base - most likely it has the hole for it on the front of the base. The sight base will be removed and reinstalled anyway for the threading.
A short cut on the stock is to get a Bulgarian blonde stock which will fit. Any new stock requires fitting because the tenon is made big so you can get a tight fit. You'll have to do some sanding on the tenon but you should have no trouble fitting it. Whatever you do, don't alter or get rid of the gas tube or original hand guards. The gas tube is valuable because it has the hand guard clips on it. This allows wood hand guards to be used on an AMD65, where otherwise you have to make a short gas tube out of a regular one to do that. The hand guards are also valuable because they are getting rare. Don't stain them or modify in any way. Regular AK hand guards fit in case you want to try something different. You should be able to find the correct wood pistol grip as it is the same grip used on the AMD 65s (some AMD65s have gray plastic grips).
But the bottom line is, you have bought one of the finest factory-made AKs ever imported. It was made 100% in Hungary and imported as a complete rifle. You'll have to bring it into 922r compliance after putting on the buttstock and pistol grip. Typically, you install a single-hook Tapco G2 trigger set and use a USA-made magazine.