Smashed iPhone 4S-Out of warranty replacement

I dropped my iPhone 4S and the screen has stopped working as well as the back being cracked. The phone itself is still working - I've been making calls via Siri; have been recieving texts and can play music etc. I haven't had the phone for very long, but I understand that the damage is not covered by the warranty I still have. I've contacted Apple and they have said I can get a complete replacement, which will be refurbished or 'as new', for £146 if I send my phone to them. My question is, is this worth it?

I assume the replacement will have the same specs. i.e. 16GB; white. But I was wondering what the actual condition of the refurbished phones are like? Do they have scratches etc? As mine was absolutely mint condition before the accident! In your opinion, are refurbs. better than 'brand new' untested phones?

Will I still have the rest of my year's warranty if I get it replaced or will I get a complete year again, or will replacing it void any warranty? As I don't want to get a replacement which has an issue that I didn't create which would usually be covered by the warranty, and not be able to get fixed for free by Apple.

Also, do I get to keep my orignial iPhone box, or do I need to send that off? And how long does the entire process take?

I've been to a phone shop and they said they will replace the screen and the back for £60, however, until they open it up, they do not know if there is any internal damage (which I'm worried about!) - for all I know, I've damaged the camera and who knows what else! As I'm sure if I get it tampered with at a shop, I will void my warranty and won't be able to get it replaced at all by Apple.

Thank you!