OC 1.5.x - How to remove steps 2 & 4 from checkout?

Hi, can someone please tell me how to remove the following steps from checkout?

Step 2: Billing Details
"Billing Details" and "Delivery Details" should be the same for my customers. Therefore, I only need to ask this once via "Step 3: Delivery Details"

Step 4: Delivery Method
Delivery is $5 flat rate OR free for transactions over $80. Therefore, I need to calculate this automatically rather than ask the customer at checkout.

I've had a good look through the code and tried a few things, but not having any luck.

Thanks
Matt

Ive actually just been doing this for a few clients and have done a custom version for the paypal express mod.. so when I get a grip on it all I will be able to post a tutorial or perhaps a script to allow it.

Thanks Q, looking forward to see the script when you have it all sorted!

I think it will make a nice improvement to the default checkout process