This is debateable, but going from Deore LX to SRAM X7 is actually a step down in terms of quality... It is unlikely that your shifters and derailleurs were 'worn out,' except maybe the jockey wheels on the rear d, which is a ~$20 fix at most... if you step into your time machine you can go back and advise yourself to change cassette, chain, cables and housing, and rear d jockey wheels and the bike will run like new.

Time machine not working either? Geez - you should take better care of your equipment ... no matter, X7 is decent stuff and replacing the crank (as others said, replacing chainrings is not usually cost effective), derailleurs, cassette, chain, shifters and cables will essentially give you a new bike. And it will be 9speed to boot!
Quality never goes out of style.

PS. Most good quality cranksets now use an integrated BB spindle (pressed into right side crank, clamped into left during assembly) and need a new BB to match... which is often, but not always, included with crank purchase.

Luckily, most monutain bike parts and frames generally have the same sizes and standards they did fourteen years ago, so you should be able to use most modern mtb parts without problem.