Looked at the plan in the Model Railroader Track Plan Data Base. I normally recommend reduction to 2/3 or 3/4 when reproducing a HO plan in N Scale. No reduction except for appropriate track spacing is usually best. However that plan looks like it could work at 1/2 (50%).
The minimum radius would be 15 inches, which is probably a little tight even for N scale passenger trains but workable.
The basic layout footprint would be 5 ft x 10 ft. The access openings and operators area could be closed and sceniced. The layout could be built in a minimum 10 ft x 12 ft room with the upper industrial area against the wall, a 2 ft min access aisle on the left side and along the bottom, and min 3 ft wide operators aisle on the right side. Wider aisles would be better. First priority for widening, the operators aisle. It would also be better if there were an access aisle along the top.
The layout would have to be built with flex track and while some adjustment would be necessary PECO curved switches could probably work.
I don't know the OP's experience, but based on his posts he appears to be a novice. I suggest he start out with a much simpler plan. Although I have been in the hobby almost 50 years, I would not try to build this complicated a layout without a lot of mostly experienced help.
