How to Program Ringtone downloads from an ASP.NET site to Mobile Phones?

I would like to allow users to purchase and download ringtones from an ASP.NET(C#) website.  I am new to WAP/WML/SMS/MMS and am not sure how to proceed.  

Customers would be limited to U.S. and Canada.  When a user has purchased a ringtone, I plan to give them a link where they can enter their Mobile Server Provider, Phone Model, and Phone Number...  

1) What alternatives do I have to get the ringtone to the purchaser's phone and what are the pros and cons?

a) Should I send the ringtone in an SMS (or MMS) message?  
Would I be sending the ringtone file itself or the merely a download link?  
If I am sending the actual file, do I need to convert it to some other format?
Do I need a WAPsite in this scenario?

b) Should I send the link to a WAPsite in an SMS message where the phone user could select a download link?

2) How do I send an SMS (MMS) message?  
Is the purchaser's cell number and service provider all I need to build the address?
Do I need to subscribe to a 3rd party SMS gateway to actually send the messages?  Are these services expensive?  Would I be posting a 3rd party form or calling a webservice?  Would the 3rd party gateway provide the how to information?

3) What is entailed in setting up a WAPsite?  
I know they are coded with WML, but do I need any special server hardware or software?

4) How do I determine which service provider I can support?

I know this is a lot of questions, but I am hoping someone can set me on the right course with a set of steps or a how to guide.  

Thanks.