Hi John,
Welcome! Hope you enjoy your build.
To your final question - I decided to fit the engine first, followed by the front suspension - a method pioneered by Chris Collins (I believe). My reasoning was simply that fitting the engine is by far (in my opinion) the riskiest operation of the whole build. With 180kg of engine weight suspended by a hoist on wheels, I wanted to limit the damage if anything went wrong. Secondly, the ability to move around the chassis and get clear visibility of the engine, bell housing, gearbox clearances to the chassis rails is important - so again my thinking was not to obscure any sight line with other components fitted before the engine went in. Either way is possible, of course - it's just personal preference!
Best of luck.