Hey guys, thinking about getting a new engine in my car (f20b DOHC vtec) but i have a few questions

1) will my CAI and Headers work on the new engine or will they not fit anymore?
2) the redline goes past what the stock gauge cluster shows, is there a different cluster i can swap in / what are my options?
3) i found this engine locally from a reputable JDM engine import business for $800 u.s., what do you guys think?
4) From what i have read this engine is an easy swap, its still OBD2 and everything bolts up easily, correct?
5) How big an improvement is this over my current setup (is it really really worth it?)

Thanks for any answers!