Hello Mehdi
When it comes to the configuration of MPLS Layer 3 VPN, you must choose a single method of exchanging routes between the CE and the PE. In the MPLS Layer 3 VPN Configuration lesson, for example, eBGP is used for this purpose.
Now, don’t confuse the peering between the PE and CE routers with the peerings within the MPLS core which are iBGP peerings within AS 234. The no neighbor command is used only within the IPv4 address family and only for the peerings between PE1 and PE3, not with the CE. Its purpose is to ensure that IPv4 routes will not be exchanged, but only VPNv4 routes will be exchanged, which is a different address family.
So if you want to create a topology where eBGP peerings exist between the CE and PE routers, just follow along in the MPLS Layer 3 VPN Configuration lesson and you should be OK. If you get stuck in something specific, let us know so we can help you out.
I hope this has been helpful!
Laz