Is it ok to use an amp that has 100 more wats than my sub? ?

Yes it is if you want to run the risk of causing damage to your speakers.

If it's 500 vs 600 or something comparable that's fine.  If it's 100 vs 200, that could be a problem.  Power output of an amp varies greatly -- it may be rated for 500w rms, but playing music its actual output would be significantly lower.  That is why overpowering speakers (within reason) usually doesn't create a problem.

Go ahead, but avoid pushing it too far to the point that you damage your speakers.

i would ask a mechanic about it

If you set the "gain" low enough and are careful with the volume knob, yes.

i would ask a mechanic about it

That depends on if the wattage is per channel or total wattage. If an amp doesn't say it's per channel but just claims to be, say, a 200 watt amp, if it's 8 channels, then that's 200 wats divided 8 ways. If the amp has a bass channel for a subwoofer, then you need to look at the amp's specs to see what the wattage output of that subwoofer channel is as it's often a higher amperage than to the rest of the channels.

That said, if you use an amp whose subwoofer channel is truly rated 100 watts higher than your subwoofer is rated, it is OK to use that subwoofer because the wattage is peak wattage. That means 100 watts is just what will go to that subwoofer if you crank the bass on the amp all the way up, so if you are just really careful about not turning the bass up to high on the amp, figuring out at which point it starts to distort and then just being religious about keeping it turned down to a level below that point, your subwoofer will be fine. The risk, though, is if some numbskull comes along and not knowing just cranks up the bass on the amp and blows the subwoofer, or even maybe bumping or fiddling with the knob when it's off, so you, not realizing the bass is cranked up, blow the subwoofer the next time you turn it on. Those are the risks of using an overpowered amp, but they're manageable risks so long as you're careful.

By the way, if it's a choice between an overpowered amp and an underpowered amp, always go with overpowered. Yes, there's risk involved, but an underpowered amp always sounds like garbage through the speakers because the power it's putting to the speakers frequently falls below the minimum required to properly drive those speakers, required to get the speakers to perform as they should. Preferably, your speaker wattage and per channel amp wattage will correspond, but if that's not an option and the choice is the amp wattage being somewhat higher than the speaker wattage or somewhat lower than the speaker wattage, go with higher and just take care not to blow the speakers by cranking the cranking the volume too high.