Shooting indoors at an arena...

So, I think I'm in trouble here... looking at my lens selection I'm not sure I have the right gear for this...

This weekend I'm going to be shooting a Lawnmower Race (exhibition)/Monster Truck show/whatever else they have going on that day... It's going to be indoors at an arena so I don't really have control over the lighting and such. Although, I will be down on the arena floor (I'm one of the lawnmower racers ) so I'll have a good angle to shoot from.

I'm debating on what to do... I have a 50mm 1.8 in my selection of lenses, but I don't feel I'll get the range I'd like from it (I don't want to get to close to the Monster Trucks)... but my other lenses I feel are too slow for the action... I'm considering cranking my ISO up and hoping for the best, but I'd hate to miss a shot...

How do you go about making sure you get the shot the first time? I'd like to play it safe, but I'm not really going to have any practice shots of the trucks... the lawnmowers, possibly... but not the trucks... (actually, my buddy may be taking shots of the lawnmowers... but we'll see... I'd rather be out there racing...)

Any advice? (other than buy a new lens quick )

don't you really want to buy an 85 1.8???????

I want to buy ALOT of different lenses... but financially, I just can't afford a new lens by this weekend... maybe towards the end of February... but not until then...

So, I have to make due with what I have and do the best I can...

Well if the new lens is out for right now can you shoot in raw and kick up the ISO?

That's what I'm thinking... although I may end up shooting in JPG... I *had* two 1 gb cards for the show, but one has grown feet and I can't find it... so, I'm limited to 1 card... high ISO... and hopefully a bit of luck...