[Closed] XTR M970 outer chainring ring bolts / general drivetrain question?

I've managed to round one of these off plus I now need a new middle and inner chainring.

Bolts £20 + middle £67 + inner £18 = £105

Question is, can I use any old outer chainring bolts on this crank?

I've got a few hanging around the garage somewhere but if I can't use these I'm tempted to just buy a brand new SLX crank (£88 for double & bash) and sell the arms on separately.

Also, if I get new chainrings, do you think I'll need a new cassette; I'd assume a new chain would be needed either way.