If you rebuild the engine head gasket, i am sure AC compressor have been disconnected and all AC gas is gone out. Just get the normal freon (AC gas) top-up from any good AC workshop and you will be fine. Galloper is very strong and reliable car. I had once for 3 years and loved it thoroughly.
the fuse always is the first one to take the wrong that may or will happen with the car so if fuse is failing for more then once then this means that there is something that needs your attention. take the car to show it to a reputed workshop and get the problem diagnosed.
'08 models were recalled for a fuel pump defect, but some 2007 models also reported probs. 2009 models haven't had the same problem, but you never know
if diagnostics at the dealer don't show a prob, my guess its mechanical. Though u got one so change it and see if it help or else see the dealer for recall.
for changing filter see the linkbelow
http://www.elantraxd.com/DIY/fuel.php
Your AC filter sounds choked, its time to replace it. Smell will go for sure, if cooling remain same then also check the AC gas leak and then top up gas after fixing the leak.
Its usually after 40k or 50k kms, if in doubt its always better to change as its cheap and not very expensive art but do good favor of engine by supplying clan fuel.
You need to chcek engine with OBD II compliance tool to read the error code and figure out what is wrong. You can get this diagnostic done in almost any shop in shj or dubai for less than 200 dhs.