Outer Limits 4x4 Board

Hi guys this is my 1st post but need a bit of help with a few things as i just purchased my 1st jeep and am fairly new to 4wd's. Got it cheep as it came through work as a trade in, so im not to worried about spending a bit of money on it. Took it 4wd'n on da weekend and was actually suprised by it's ability straight outa the box.. though i wouldnt mind knowing what to tinker with 1st.
My questions are as follows..
1. How much a lift can i go before changing/modifying everything? (i would like to fit decent rubber, say 32inch)
2. What tyres could i use for both off-on road without changing tyres every 10,000 kms..?
3. The muffler has a hole in it so the 1st thing i'lll b doin is changing the complete exhaust, should i go a 2.5inch mandrel or is there a better option?
4. Do i have to change diff ratios when going to the tyre size i mentioned?
5. How do the engines cope wth gas conversions as i would like to tow the boat from vic to n.s.w a fair bit and the cost of fuel would be slashed somewhat.

Thats about it 4 now, feel free to add any info that ddoesnt relate to the questions. By the way its an auto.

XJ96jeep,

you can go 2.5-3.0" susp lift max before you need SYE, extend brake lines etc 31s are okay with this lift. 32s and bigger will require ratio changes and all sorts of shit. also can create more strain and wear on hubs, wheel bearings, uni etc. (there expensive to replace and/or upgrade). cant do body lifts cos of monocorque body (no chasis) only suspension, so >3" lift can get real expensive depending on if you can do it yourself. a good site to check out is http://www.go.jeep-xj.info/

havent changed the exhaust on mine yet, but heard the 2.5" systems with extractors are the go