It took me 15 years to pay off my student loans, so I can relate. If you are looking for a replacement engine with a modest increase in power I would suggest a GM 5.3 V8 from Motech. Your Jeep will cost $15K, and a 5.3 swap cost just under $14K, so that gets you into a V8 JKU for under $30K. If you are looking for a big increase in power then you'll need to consider a GM 6.2, or even a 6.4 Hemi, which is what I have. The price goes up considerably with the power increase, but the fun factor of driving that Jeep goes through the roof.