Looking to do ubers on single player with a budget necro (have shako/arach/magi already) but looking for a guide including skill setup/strategy

I'm not sure if it can be done with a budget necro. Without enigma your minions go wherever they want, and you are very slow getting revives. Anyway if you want to try you just need a lot of urdar and similar enemies: https://diablo2.diablowiki.net/Blunderbore

I have a naj staff for teleport. I'm finding it ok to do the bosses while merc is alive and I have urdar revives up however trying to keep merc alive for Mephisto I'm finding near impossible. Anyone got any ideas?

It's allways hard to keep merc alive in ubers without feeding him a lot of rejuvenation potions.
Are you using decrepify as curse? What items is your merc using?

Merc is using gface eth obedience mancatcher and eth duress and yes using decrepify. I find he gets killed before I even have the chance to rejuv

You could use kiras with ort to boost his res, and other armor with more res. You should focus on urdars for crushing blow.