1987 TRX250 – need advice

I picked this up for $525 and pulled the engine cause she ran awful and smoked like crazy. I never checked timing (stupid me) only valve gap and pulled the top end apart. I do have a service manual.
1) how can you tell if rings are bad? How does one measure ring gap? Mine look good but this quad smoked real bad!
2) I plan to replace valve seals but looks like one valve guide is cracked. Do I need to order the special tools to replace the guide and ream? I hate to buy a tool I’ll use once.
3) The timing chain seems a little lose, not wanting to dump too much $ into this, how can I tell if it’s too lose and where can I get a quality aftermarket to save $?
Thanks all