I looked at Tech when getting mine, I ended up with a Parweld as there seemed to be fewer stories of failures, and it is a relatively older brand - R tech have good customer service, but I would rather not have to use it at all.
Cam is common sense and workshop manual, plus the break in procedure, you do need to remove the radiator and all the front accessories, and inlet to do it, but doable in a day if experienced.
Biggest fight may be seized bolts, particularly the water pump, but it is all soluble.
Yes, and anythings possible I guess, I read somewhere it is the cat, and needs to be as slowe as possible to engine for heat/efficiency reasons, so they couldn't move it without getting the whole engine reassessed for emissions, and therefore massive costs.
Sounds plausible, but unsure exactly how true it is.
Avoid RPI....
Standard ignition in good order is perfectly fine unless you like drowning your engine.
Personally I would get a wideband lambda fitted, it is the only really reliable way to know what the engine is doing when driving about.
Every time I have ever done that with a stock ecu they just don't run quite right.... MS obviously is no problem but for a stock ecu the dead time of modern injectors are much lower so mess with the low speed fuelling.
Yeah, no point connecting both, the whole idea is to draw clean air through the crankcase, either one is fine, whichever gives neater hoses.
And yup, a small mushroom / pod style filter will be fine.
Find the large port that enters the throttle body above the throttle blades and connect it a pipe there.
Connect it to one of the rocker covers.
On the other rocker cover fit a small filter.
Then the engine only breathes the ending fumes when you have the throttle open (so not at idle).
Run it like that for a while and see how it goes, it should be fine, and prevent too much oil build up in intake.