I am new to this forum and mountain biking so here is my question. I have an old Specialized Hard Rock from about 15 years ago. The frame is in good shape but it has been pretty neglected over the past 10 years or so. I am looking at getting into mountain biking seriously/semi seriously. My question is what should I look at getting to replace the components, what components should be replaced, and is it worth the time and money to replace or would I be better off buying a new entry/mid level bike? I am not looking for high end components but also don't want anything super cheap. So any advice is welcome. Thank you in advance!
if the bike is comfortable to ride then you are all good.
get some kool stop brake pads. pretty inexpensive.
get a bike maintenance book. bikes are really easy to work on. if you have a book to refer to then you wont have to run to the bike shop every time you need your mech adjusted.
cables and housings. these will likely benefit from replacement. the book will tell you how to do it. no special tools involved.
the only part of you bike that is probably pants is the suspension fork if it has one. suspension forks are stupid expensive and not worth looking at until you have a pretty good idea of what you need. if you have a rigid fork, then that is awesome. stay with that. if you have an old pantsy suspension fork... just ride it.
tires. get some tires for your old bike. you can get a front and rear set of irc mythos for 40 bucks. those will do the job.
the rest of the components on your bike are not all that different from nice fly new components. they just need to be looked after a little better. that's what the maintenance book is for.