What happens when you return a MacBook with upgrades installed?

I have a mid-2012 MacBook Pro which I recently upgraded from 4 to 8GB of RAM and put a 240GB SSD in. I know that this doesn't void the warranty by itself. My question is, if it breaks and I take it to an Apple store with these upgrades in place, do they switch my bits over to the replacement MacBook, or at least give you the new Macbook sans RAM & HDD, or would I have to return it to factory spec before returning? I've not been able to find out anything about this online.

The reason I want to know is that I'd like to stick my 500GB into a caddy, and someone has offered to buy my old 4GB of RAM. If I'd have to put my old bits into it before returning it, I won't do anything with them and keep them aside, just in case.

Thanks

 

If that's the case, I'll probably keep the old stuff aside in case I need to return it. Hopefully it won't break, but it's good to know exactly what I need to do if it does. I suppose if they were replacing it with a machine of much higher spec, I wouldn't mind too much about losing the upgrades though

I think that's what I'll do; makes sense to keep the 4GB spare as well I suppose. The HDD though, I think I'll still stick that in a caddy for portable use. I can always put it back into the MacBook if need be.