I have an oil leak at the front of my motor under the timing cover of my 1998 Tracker with 1.6L motor.   From what I read it is an oil seal. 

Am I correct to assume this?
How hard are they to replace (time and expertise)?

Yeah, most likely a crank or cam seal... possibly oil pump gasket, but that's less likely. These seals are behind the timing belt cogs & are often replaced along with the water pump when doing a t-belt job.

It could be the oil pan leaking too, since that is right under the bottom of the timing belt cover and can make it appear that oil is coming out from under the cover.  But oil pan leaks at the front of the engine aren't as common as cam and crank seal leaks.
Replacing the cam and crank seals isn't too hard to do.  You have to remove a lot of stuff to get to them though....crank pulley, alternator/fan belt, AC/PS belt, timing belt cover, timing belt, cam pulley, plate behind cam pulley, lower timing belt cog.  Then you remove the seals (I use a sharp pointed drywall screw and screw it through the outer face of the seal, then use some pliers to pull on the screw to pop the seal out).
The seals aren't that expensive and the same seal fits both the cam and crank.
If you aren't that familar with taking the stuff off that I mentioned, I'd plan on a full day of removing, replacing the seals and putting everything back together.

Do I have to drain the oil to do the job?  I was reading in the repair manual about replacing one of the seals and it said to drain the oil,

Do I have to drain the oil to do the job?  I was reading in the repair manual about replacing one of the seals and it said to drain the oil,

No, you don't need to drain the oil.  You may get a little oil that runs out, when you pull the seals, but it's not like all the oil will run out.