i'm not an expert here so please forgive me with my noob questions. i got an Ultimate Wall-E robot toy for my 2 boys. it looks ok but i think it needs some modding.

like.. the nicad battery pack is small like 6 cells (double A size cells) and gets easily drain.

1) can we use lipo 7.4 battery packs in it.
2) can we make room inside its compartment to place an extra battery pack?
3) i also think the thread wheels doesn't have bearings, so plastic bearing make it a major drag and helps drain battery life faster
4) i was hoping someone would help and make some instructions as to incorporating metal bearings in it just like in our r/c cars.
5) does lipo battery packs only good for brushless motors? can i use a parallel wiring for two lipo packs to wall-e. no harm could be done?
5) anymore modding ideas is much more welcome. and thanks in advance.