Domino and IIS together

I am an primarily a Notes developer (with 4-1/2 years of development experience) but am now doing some administration.

We have developed an intranet Web-enabled Domino application on Release 5.03. My client now wants to separate the data (Domino server) and the HTTP stack by integrating Domino and IIS and making Domino use the HTTP stack of IIS4.0 This is so that additional security can be introduced by having a firewall implemented between the two servers (Domino and IIS).

Here are my questions. I hope they're not too banal. I am quite a novice when it comes to administration.

1) Is the above possible? Will it indeed provide additional security?

2) If the above is possible for implementing the firewall, will Domino and IIS have to be hosted on separate machines?

3) If a firewall can be introduced when Domino and IIS are on the same machine, how that can be accomplished?