ASP Software

I am currently using a mixture of Dreamweaver, Fireworks and Flash on my business web site but am interested in saving myself time (longterm) by moving into ASP. What software would I need to program in ASP (as I know nothing of it), who makes it, do I need an ASP cabable server or will my ISP supply it and what else is involved?

Is ASP worthwhile or for a medium size business site of 250+ pages what would people suggest.

Thanks
Bruce