IE BHO: How to Inject External Javascript file?

Question

I am now porting one of my extensions to IE. It will be done in C#. I am looking for some smooth transition. My Chrome based extension does following once the page is loaded:

1. Inject Script Tag having src of external JS file
2. Inject CSS Style Link that will style the markup
3. Insert HTML based DIV that will have some listeners like closing of DIV etc.

It was easier to do in Chrome but I guess IE has a separate route. I know I can use IHTMLElement and other stuff to manipulate DOM but I want to keep my code standarized. Atleast the one dealing with DOM. Can it be done at IE part?

Thanks