i about to clean the cpu and heatsink and reaply thermal paste

is alchool 70% good enough to take out the old thermal paste or shouild i get some higher one

The alcohol you have is fine. Just get a soft cloth and carefully wipe the heatsink and the top of the cpu clean. Reapply new paste sparingly.

run out to your local grocery store and get some 90%+... it hardly costs anything.. and will leave less residue.

While your at the grocery, buy some distilled water and clean off the alcohol residue.

Without being too anal about it, just use the 70% stuff. Apply it to a cloth and rub the goop off the cpu. Try not to get any liquid on the motherboard. Repeat the cleaning process using a clean part of the cloth until all the paste is gone. Let it dry completely and then apply the new paste.

You don't need to overdo it. While I probably should have used a cleaner, I took a dry paper towel and wiped it down when I reseated my HS, and it is working well. Just try to be thorough about it.

I just ordered some special CPU cleaner along with my new thermal paste, no idea how good it works but it seemed a good idea at the time. It was called Akasa Heatsink + CPU cleaner or something, I'll tell you how well it works once I've used it.