It's all doable - but you have to ask yourself why you would dilute your billable design hours doing something you would have to go thru a huge learning curve just to get basic knowledge.
Are you comfortable billing clients for sysadmin tasks when you're a raw beginner? What excuse will you give them when their sites are hacked or brought down?
Most small businesses fail because they lose focus on what makes them money - will sysadmining make you money, or just cost you lots of time and grief?
If you've outgrown shared hosting (and who hasn't) perhaps you need to partner up with a developer/sysadmin and combine your talents.
Always remember, security is a ongoing (never ending) process, not a one shot procedure.
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Either provide enough details for people to help, or sit back and listen to the
crickets chirp.
Security thru obscurity is a myth - and really really annoying.