gasket sealant confusion

[msethk]

i have searched and researched for the last 4 or so hours and am really confused. I am installing a thermostat on a 1994 c280. i want to make sure to have everything i need before i start. I see many posts that call for loctite 5900 sealand or even 5970. i have also seen something called permatek "right stuff." I called the dealer and they brushed me away from the purchase of the mb brand sealand because it is $39 for a small tube and was referred to pep boys to find a permatek brand (nice, what an awesome salesperson... if i were his boss i would have fired him... there goes his comission..hehe) what should i use for the sealant?

thanks