Need suggeestions for repairs -- '88 5kCSTQ

[wenode@perelandra.cms.udel.edu (Vinod Arekar)]

I have on the '88 5kCSTQ:
1. Hole (2.5cm dia) in the muffler
2. A leak in the central hydraulic pump
3. A leak in the radiator
4. 99k miles

	The mechanic said the central hydraulic pump leak might be just
a bad O-ring at a screw (I hope so!). The dealer cost for all this is very 
high (like 400$ for radiator etc.). How good are the mailorder parts?
I read last week that a mailorder co. in Chicagoland has metal ends 
radiator for 135$ (+ shipping)! I'm especially concerned about the 
muffler since I've heard that the non-factory mufflers may be noisy.
Warranty is another concern. Before I spend a good # of 100$s I wanted to
findout if I was doing the right thing, so please let me know of your 
good/bad/ugly experiences of mailorder parts, especially the ones I need.

	Another thing I was thinking of doing was putting synthetic 
(redline or so) fluid so I'll have smoother shifting. Any suggestions
about good brands?

	Thank you.

	Vinod