if you buy a tank with metal gears does that mean they are the 3/1 version ??/ i mean the ones that are slower but more powerfull

No, there just like the plastic ones.

how much are the 3/1 gears and are they easy to install

Contact. blueslatesman on e-bay. He usually has them. They are not very expensive and it is only a matter of swapping the gear boxes. 4 wires thats all.

about those 4 wires do you have to re solder them

You can get High Torque gearboxes for about £45. I've just fitted some to my Tiger and they're great.

i know i cant mention this site umm tankzone haha anyways there are selling them for 40

Toyzcastle (ebay) has them for £24.99 / $46USD (item 110263189656)