Where to get started Modding

The bed should only shake if you're over extruding. Glass is one of the cheapest and easiest mods you can do.  Printing an MK-4 or 5 is free and will be greatly appreciated when you need to clean your nozzle.  The E3D will allow you to print other materials.  The bulldogXL geared extruder will eliminate moire.  As far as switching belts I think you would see better results by switching to spectra line.  Putting a well-nut on the z-screw provides great enhancement for little cost.  All of these things can be found here on the forum if you search.
Hope this helps

You can use cheap glass from any hardware store cut to size.  I've been using the same piece for 8 months now all for about $5

okay canceled that order, I'll probably go to the local ace hardware and see if they can cut me an 8x8 piece.

Printing another extruder is the next thing you should do, because the acrylic is prone to breaking.  But first look into calibrating your flow rate, because extruding too much plastic will affect the dimensions and fit.

+1

I got a 4 pack of 8x8 frames at Michael's Artist Supplies for $12.  The glass is a perfect 8"x8", and is only 1/16" thick.  4 months later I'm still using the first piece.  No scratches or chips.

Gotta go into the store.