Sql Server 2008 Web Edition is advertised by MS at $15 per month. I want to run this on my servers instead of the current sql express.

Would it be possible to buy these licenses off TP ?

Otherwise buying it is a nightmare, I spent hours searching for a MS reseller that would sell it, and there's hundreds listed but none of them have online purchase or even any indication that they sell it..

SQL Server 2008 Web Edition is available for $25 per physical processor. I just spoke with a sales rep about the process for provisioning it on your server, and he said that he'd open a ticket on your account with details (6005851PLNT).

I think it's a relatively painless process, but I don't know how difficult the transition would be from SQL Express to SQL Server 2008 Web Edition ... Chris will have a much better idea of what it entails.

There is no upgrade path to MSSQL 2008 Web. This would have to be a separate MSSQL instance installation. From there, the databases can be imported to the new instance from backups of the express instance.

can this be done seamlessly, or is there any risk of compatibility issues and things dependent on those databases to start having problems?

Its a 10 minute job. Backup your databases, remove express edition, install web edition, restore your databases with force/overwrite ticked. thats it.

very simple stuff