[R] R-1.8.1-4: Font family, ticks and mathematical expression??

[Pisut Tempatarachoke]

Hi all,

Could anyone help answer the following questions, please?
(I'm using R-1.8.1-4 on Fedora Core 1 and very new to R)

(i) Is it possible to specify a font family (e.g. courier or helvetica) 
when graphing?

(ii) How can I make ticks point inwards on all four sides of a plot?  Is 
it possible to have minor and major ticks?

(iii) How would I specify a symbol "\sim" (i.e. "~") in a mathematical 
expression?  So far, I've only seen "%~~%", but that's not exactly what 
I'm after.  (I tried "%~%" but that didn't work.)

Thanks so much in advance, everyone.

Regards
Tempo