Clearskies March

I am definately NOT a newbie

Hello, I got my heart broken and left SL for a few years and came back to a whole new world! I have so much invested in old school primmy clothing, hair, etc. I am dragging my feet on going mesh. I don't mind the expense but it's the whole idea of parting with some of my things that are genuinely antique and made by creators who are no longer inworld. I need someone to educate me on fixed mesh and why I need it. I go places and can't see avatars made of mesh and I was given some alpha masks but when I put them on I'm invisible? I even had to use the Firestorm viewer because my laptop is truly a piece of crap. I understand that excessive prim usage creates lag and nobody likes that but someone PLEASE explain to me why I should go mesh. Are most residents using it now and how do I even begin? I'd love to sell some of my fabulous antique items if anyone can point me in the right direction. Thanks in advance! Clearskies