o2 sensor question

im turbo charging an LS (b18b1) for my crx. this LS motor is obd 1, but i have wired it up as obd 0 so that it will work with the obd 0 crx wiring. when i bought the LS it didnt have o2 sensors, so i have to buy them.

1) how many o2 sensors are there supposed to be for my set up? (i see a hole in the exhaust manifold for one, but are there any others)

2) when i get the turbo kit (probably drag 3), will my set up still require the same # of o2 sensors? and will they be located in the same place(s)?

3) since i have to get new o2 sensor(s), which type and/or name brand is best for a turbo set up? (i.e. High temp o2 sensor) and where can i get it from?

4) how much should i expect to pay? and is the wiring up of the o2
sensor(s) difficult?

thanks