Char, I am a beginner with this too, but this is what I have learned about it since reading this forum.
1. I don't think the temp *has* to be a whole 175, but it needs to be liquid form. If the butter is grainy tho, you may want to hold the 175 temp for 20 minutes so it doesn't become grainy.
2. A few minutes (five seems common)- or trial and error. Different suppliers, different temp inside your house should be noted just in case. The first time it should still be pretty much liquid.
3. Freeze the same amount of time as you whipped it. You will want to see a very light 'skin' around the edge from where it is getting solid again.
4. yes, mix again... you'll repeat this 2-4 until it's done. How many times depend on the amount you are mixing.
5. I add the oil after the shea has melted but before whipping.. Some may add it while melting the shea, but definately before whipping.
Also, you can always fill your sink with ice and water, making an ice bath. The point of freezing it is you want the temp of the shea/oil to lower and solidify fairly quickly. Whipping in an ice bath the whole time may be better to start so you can watch the whole change take place.
HTH