Yours is a very hard question to address because don't fully understand what your final configuration will need nor understand how well you know how to configure Cisco devices.
Starting with a racked and connected 4507, in my current environment, it would take me between 4 to 16 business hours to fully configure it for production. However, I work with predefined templates, which only require I "fill in" things like IP assignments. (Much of my noted time would actually be involved with the "paperwork" for a new 4500 deployment.)
Starting from scratch, I could probably provide a "working" 4507 in 4 to 24 hours, but it might take weeks to work through all the other configuration options. Again, much depends on your configuration needs.
To just give you an tip of the iceberg view, if you're going to do L2 between your 4507 and Junipers, you have issues dealing with VLAN1 and STP between the vendors. Or, also if doing L2, you have the option of running some flavor of VTP between all your Cisco devices (if they have Cisco connections), but not with your Juniper devices. Or, Cisco, by default, does CDP and Juniper does LLDP, although the later Cisco platforms can enable support for LLDP.
You might want to retain a network consultant, familiar with both Cisco and Juniper, to help you work through the configuration options. Such a consultant, with more detailed knowledge, should be better able to estimate the amount of work needed.
