Like I told you earlier creating an emulator isn't something easy.
Especially when you start from scratch. You need a good understanding of an programming language and get familiair with the tcp/ip networking stuff. Once you've understand the networking process you can start digging into the packets of silkroad. It might look like a lot abracadabra now but believe me if you learnt some network stuff and now how to sniff packets it starts to make more sense.
I recommend you to buy some good books about the language you would like to learn or find a really good online resource.
If you aren't going to start from scratch but use an open source emulator it would still require you to know how to program and to expand that emulator you have to know network sniffing/programming. and it will probably take some time to know how the data flows through that emulator cause most (if not all) open source emulators doesn't have very much comment in their code.
about that client I don't know where to get it. but you might try to just download the latest one get your open source emulator and once you know how to program you start updating it cause the first few packets doesn't change(or at least in isro they haven't changed for a while but i'm not really long in the network scene so i can't really tell you that).
btw the most important thing what you need is FREE TIME a lot of free time