You might be able to find like a used Drag or revhard for that much. But it's probably not gonna have everything you'll need for a properly running turbo. You could do a HMT or "junkyard" setup to try and keep costs down. With this kind of setup typically people use T3 turbos, intercoolers, BOVs, and injectors out of OEM turbo cars. You'll probably only see between 200-250 WHP with this type of setup.

350-450 WHP is going to need a LOT of work done to the engine not to mention higher quality turbo parts. You're not gonna be able to do it with your average junkyard turbo. Maybe on a used T3/60-1 or T61 but those are a little expensive. You could just get a used T04E 50-60 trim turbo, but you'll be maxing them out to get to 350 WHP. If you're looking to make 350-450 WHP look to spend anywhere between $3000-$5000 for a good setup, plus another $1500-$2000 for upgraded pistons and rods.

Now as far as installation goes, a turbo install is pretty easy. It's kinda like you are doing an intake and header install, along with fuel injectors and a fuel pump, and some minor wiring. There are enough how-to threads on honda-tech to help you out in that area.

EDIT: as far as pricing goes you can probably find used T3/T04B or E's for $200-$300. Used log manifolds can be bought for $200-$400. A used downpipe can be found for around $100-$200, used deltagate or TIAL wastegate for $80-$160. A new johnnyracecar.com intercooler is around $200-$250. IC piping is around $100-$150, a 1G DSM BOV (I think 1st Gens are the good one) can be found for $20-$40. DSM 450 injectors which are good for up to ~300HP can be found for $40-80. You can be up and running with CromeFREE or Uberdata for about $150-$200, add another $300-$400 if you need to buy a laptop for tuning.

DOUBLE EDIT: opps, didn't see your post about already having hte turbo. Do you know what the turbo specs are? compressor trim and a/r and the turbine a/r?