2 Price Lists needed - Retail & Wholesale

We are very new to Opencart and have started adding our products to the storefront. The default site is retail. However, we also want our wholesale customers to be able to:

1. create a wholesale account (rather than default) which we must approve before they see prices
2. see wholesale prices when logged in rather than retail prices
3. checkout only when their order reaches the required £100 minimum with a single payment method (we call them once we have pulled the order to take payment from them over the phone - so no payment integration required)

Can anyone help please as we don't have a clue?!

Most of this is built in to OpenCart. Drop me an email to jamie@clickbusinesssolutions.co.uk and I will advise as much as I can :-)