From darky's 10.1, how to EXACTLY flash back to any stock rom gt-i9000m BELL CA

Hi, I have darky's rom 10.1, for some reasons (warranty, sales or bugs/troubleshooting) I'd like to flash back to everything stock (even if it wipes/reset everything I don't care). I found absolutely no guide to doing this, but only guides for international i9000 and others (t-mobile vibrant, captivate etc). I don't know where to find my stock firmware (tar,pit etc). i'm on darkcore 2.9 kernel, jk4 modem and darky's 10.1 rom, all rooted. What would be the easiest way to flash back to a stock rom (and then I could update the cellphone via kies and sell it to my brother). Please help me guys I'm in the dark with this, any input would be very appreciated ! Also, it seems I can't get into recovery mode, no matter what I try It just won't work, fortunately though, the download mode works perfectly.

Also, since flashing to darky's I'm having some problems with the data plans (my other friend with Bell has a lot better connectivity and he never loses connection, unlike me)

edit: Not sure that's gonna help, but when I boot the phone, it's clearly written gt-i9000m, but when I go into settings>help it is gt-i9000 (maybe it's darky's rom doing it, it may be normal)

Anyway, sorry for my somewhat poor english I'm from Quebec. Thanks a lot guys!

Pls. read this guide.

Yes. My phone was locked,too.
Steps:
1. To root your phone.
2. to unlock your SIM.
3. to fix the 3 button combo if it doesn't work.
4. Download and install Odin (Windows) or Heimdall (Windows, Linux, Mac) on PC.
5. to select a ROM to flash.
Check your SIM: dial *#7465625#
What's the result?

No.
1. your phone is rooted.
2. Your SIM has to be unlocked: pls. read this.
Now you should follow the steps in that thread.

Try this:
1. disable the lagfix if enabled before now.
2. backup your data via Titanium Backup (Pro).
3. do a factory reset: menu>settings>privacy>factory data reset.

You are welcome!