Here are some references for the Part 3 essay I'm supervising this year.
Main Reference
Iwahori, N. and Matsumoto, H. On some Bruhat decomposition and the structure of the Hecke rings of p-adic Chevalley groups, Inst. Hautes Etudes Sci. Publ. Math. 25, 1965.
References on Chevalley groups
Carter, Roger W. Simple groups of Lie type, Wiley Classics Library, John Wiley & Sons, Inc., New York, 1989.
Chevalley, C. Sur certains groupes simples, Tohoku Math. J. (2), Volume 7, Number 1-2 (1955), 14-66.
References on local fields
Serre, J-P. A course in arithmetic, Translated from the French. Graduate Texts in Mathematics, No. 7. Springer-Verlag, New York-Heidelberg, 1973.
Serre, J-P. Local fields. Translated from the French by Marvin Jay Greenberg. Graduate Texts in Mathematics, 67. Springer-Verlag, New York-Berlin, 1979.
Iwasawa, K. Local class field theory, Oxford Mathematical Monographs. The Clarendon Press, Oxford University Press, New York, 1986.
References on p-adic groups and their representations
Bushnell, C. and Henniart, G. The local Langlands conjecture for GL(2), Grundlehren der Mathematischen Wissenschaften [Fundamental Principles of Mathematical Sciences] 335, Springer-Verlag, Berlin, 2006.
Kim, Ju-Lee, Supercuspidal representations: construction and exhaustion, Ottawa lectures on admissible representations of reductive p-adic groups, Fields Inst. Monogr. 26, 2009.