[suicideneil]

Welcome.
1. That is all you will require, but a selection of pinions & spurs would be ideal to allow fine tuning of the gearing- checkout Brian G's calculator.
2.The feigao & wanderer are identical except for colour, they both do 2084 rpms per kv, so using 14-16 cells would be perfect for good speed/power.
Aluminium diffs you say, I take it you mean the casing is alloy. The diffcup in side the casing should be upgraded to an alloy one using larger 3mm screws to fix the ring gear to it (sold in the RC-monster store)- you will need two for both diffs. As for the spool issue..... it will hamper your turning & steering ability alot at speed, but then again it will allow you to put 100% of the power down in a straight line (drag racing). Personally I would get a 3.3 diff from ebay and the upgraded alloy cup/ring gear from here to put into the rear axle.

Do you have a link to the item page on ebay so we can have a look-see?