Kernel update
 

I`m planing to upgrade my kernel to 2.6.38.rc or .37
so is there any good guide how to upgrade kernel in Slackware?

Have a look at Alien Bob's guide - an excellent reference.

Since you are asking how to upgrade, I would recommend using the more stable 37. rc releases may very well break. Also be sure not to overwrite your existing kernel so you have a place to fall back if something gets left out. good luck!