yep, the 2300's been on the C5s for about 4 years or so now. i got mine in 2011 straight from Magnuson.
for intakes, i grabbed the LG version of the Blackwing. works fine
i agree to stick with 1 3/4" headers unless you know you're turning it up to 11 later (or going with a bigger-cube engine).
how much boost you wanting to run? with a 98 engine, i wouldn't push more than 9-10psi. the 3.3 got me about 8.5 @ sea level & 1 7/8 headers, so i'd say that's about where you'll be with a 3.1 at your elevation.
93gas with a rich tune got me about 480 - coulda easily had >500 with a touch less fuel & another degree or two of timing, but i was just starting out & didn't want to risk it. the past couple years, i've been tuned for 11 @ sea level & it's a little more fun
you'll probably also want a 104-ish serpentine belt. the one Magnuson sends in the box is sized for a 3.6