If you open the cases you run the risk of voiding the lifetime warranty. My GG6 is 8 years old and still running strong on the original factory grease.
By the way--did you get a 5" backing plate and 5.5" pads for the GG6?
Stick with a Griots GG6 for your first polisher. Here's a write up by Mike Philips that may help--Here's what you need to get into machine polishing - Recommendations for a beginner by Mike Phillips
I've been using Megs Ultimate Fast Finish on wheels with very good durability--getting about 6 months out of one coat. It is really easy to apply to the wheels including the barrels and makes the wheels a snap to clean.
Meguiars Ultimate Fast Finish
Which ever DA you get, make sure you purchase enough pads--here's a link to an article by Mike--- How many pads do I need to buff out my car?
Here's a link to thin pads---Lake Country ThinPro Foam Pad System 5.5 Inch 6 Pack - Your Choice!
I'd stay away from prepackaged kits and put your own together. Kits usually have things you will never use. As an example the GG6 only comes with the 6" backing plate. You really don't even want to use it. Get a 5" backing plate and 5.5" Thin pads--you'll save money and the polisher will...
After soaking them in APC I clean them with LA Awesome Orange Degreaser from the Dollar Store. Doesn't get all the stain out, but gets the LSP and AIO out of the pad.
Re: Griot’s 6” RO Polisher with Meguiars Products
You will need more pads!!! How many pads do I need to buff out my car?
Get a 5" backing plate so you can use 5.5" pads