Deleting an SSP
If your question is whether you can delete an SSP that your MOSS farm is having, then the answer is Yes. But you will not be able to delete an SSP if thats the only one SSP that you have in your farm.
If you just have a single SSP in your farm, then that SSP would be the default SSP for the farm and you will not be able to delete a default SSP in the farm.
Now, improving your performance, depends on what all features you are accessing from the SSP, basically Search and crawl in the Farm. Even InfoPath services and User Profiles are dependent on SSP. Performance will be improved if your site does not have search functionality and crawling, because this is what loads data into the tempdb.
So, the fact is that you need to have atleast one SSP by default in the farm, even though all features like Search and Crawling is not used. And you should be thinking of other options like improving RAM or DB space, rather than just deleting SSPs.
You can start with reading blogs like this for performance improvements - http://blogs.msdn.com/b/sanjaynarang/archive/2009/04/18/sharepoint-performance-stress-load-testing.aspx