for 7h8p7p5 its better if u use three fingers... one technical way is to put ur index finger on 5, ring finger on 7 and little finger on 8 and play as required... I have never tried this song... somehow i never tried metallica, i guess kirk hammett's out of my league somewhat. ;P but if i had to play this i might play the 7th with my middle finger finger hammer to 8 with my ring and then slide back to 5... anyway, jayanth will probably tell u how kirk hammett plays it. There are many ways u can play the same thing and u shld always play the way u prefer.
u just pull the string off for p0... its the same as what u do only here u dont have to press any other fret.
For the final part to ur question, u should use finger picking for this song... so, play 5th string with ur thumb, 3rd with index, 2nd with middle finger....
The words of a banished king
"I swear revenge"
Filled with anger aflamed our hearts
Full of hate full of pride...
Oh, we screamed for revenge
- Blind Guardian (Nightfall)