The team from LANDesk may disagree with this (!), but we always recommend not only uninstalling the older version, but also removing the directory and it's contents. This just ensures you don't have old patch, readme type files lying around. To uninstall using SCCM, you'd need to ask your own SCCM team on how they do packaging.
As a general thought, in your situation, I'd recommend your client looks at using webdesk . They can get access to it rapidly, it's almost certainly going to be faster than console and gives them an ability to have a phased deployedent of the new console, rather than a big bang approach.