i have a 1997 4 door auto sidekick and the guy i got it from said it has 4.62s in it. he said he's ripping apart his 5 speed sidekick and that he'd give me the gears out of it which are 5.12s.....is this true that the 5 speeds and autos have different gears? would this be worth swapping out gears?

Yes, and Yes, especially if your going for bigger tires.

Some models came with 4.30 gears, so either way you would be better off with the 5.12s

Wild

sweet =D just wanted to make sure i wouldn't be wasting time when i lift it. thanks alot

Well, hold on... the 97 4dr (4spd) autos came with 5.12's sry. 
From Skyhiranger's gear post on the Zu:


                      89-98 Trackick gear ratios

Years....2 or 4 door...Engine type...Transmission...Axle ratio
89            2             1.3L carb.     5 speed man.  5.625
89-95       2             1.6L TBI       5 speed man.  5.125
89-95       2             1.6L TBI       3 speed auto  4.625
91            4             1.6L TBI      5 speed man.  5.375
91            4             1.6L TBI      3 speed auto  4.625
92-98       4             1.6L MPFI    5 speed man.  5.125
92-98       4             1.6L MPFI    3 speed auto  4.30
92-98       4             1.6L MPFI    4 speed auto  5.125
94-98       2             1.6L MPFI    5 speed man.  5.125
94-98       2             1.6L MPFI    3 speed auto  4.30
94-98       2             1.6L MPFI    4 speed auto  5.125
96-98       X90         1.6L MPFI    auto or man.  4.625

4.30 gears have a 10/43 tooth count
4.625 gears have an 8/37 tooth count
5.125 gears have an 8/41 tooth count
5.375 gears have an 8/43 tooth count
5.625 gears have an 8/45 tooth count

Unless the 4.625's were swapped in it's already got the 5.125's... the only 4dr that came with 4.625's was the TBI '91.

i have a 1997 4 door auto sidekick and the guy i got it from said it has 4.62s in it. he said he's ripping apart his 5 speed sidekick and that he'd give me the gears out of it which are 5.12s.....is this true that the 5 speeds and autos have different gears? would this be worth swapping out gears?

Yours has 5.12s.
The only factory gears that are lower (numerically higher) than 5.12s are 5.38s and 5.62s.  Both are kinda hard to find.....but I do happen to have some of each ratio for sale in the for sale section.  They are complete thirds that will bolt right into your sidekick.  But the fronts have 22 spline sidegears, so you will need to swap out the left side inner axle shaft and the right side CV shaft.

well at least i have good gears. would the be fine to run on with 29" or 30" tires?

Yeah, you should be fine, with that size of tire.