First time biasing an amp. Help.

Yes it’s dangerous to you and you can take out your amp as also.

It’s not something you ask how to do, it’s a job for a technician, or at minimum a good electronic hobbyist very detailed instructions solely for that piece of equipment.
If you don’t feel confident in doing from instructions from the many directions on the net, then really you should get someone to do it for you that has the confidence.

Biasing instructions for ARC Classic 30 at the bottom.
http://soundmovements.co.uk/diyaudio/CL30.html

Audio Research Data Base Biasing for Classic 30
https://www.arcdb.ws/Database/CL30/ARC_CL30_bias_adjustment.pdf

Cheers George

People freak out about electricity all the time, sorry, its just the way they are. This is really simple and nothing to be making such a fuss over. The last paragraph on page 7 is all you need to know. 

Set your multi-meter to amps. Put one probe in TP1 and the other in TP2. The meter should read something close to 65mA. If it does and you are happy then you are done. Bias is a trade off. There is no one right or wrong. It is not going to hurt a darn thing to run them at 60. It is nice however if they are both the same. 

So set it at 65 by slowly turning the trim screw. Which way? You will know soon enough. If it goes down when you want it to go up, guess what? Turn it the other way. It ain't rocket science. 

Do the same on TP3 and TP4. Now you really are done. But being your first time you probably want to check back and forth a couple times. You may notice the next time its 64 or 66 instead of 65. No big. All that's happening is sometimes the trim pots take a minute to settle in. Similar to why you want to have the amp on and running a good 15-20 min before doing this.

Congratulations, you've now biased a tube amp- and maybe even survived to tell the tale.

I would trust Georgehifi's assessment before others.
If you aren't sure, find a capable tech. I would bet ARC would be able to point you to one.
Bob