What motor do you have?
Oil leaks due to an impending head gasket failure show up at the rear of the head. If the leak is at the front (by the alternator as you stated), it is the timing cover seal, a much less expensive repair.
Unless you are burning several quarts of oil a month, I wouldn't bother with the valve guides. Save that job for when the head comes off for the head gasket. You are losing more oil out of that timing cover anyway.
Is the tensioner making noise? Usually, a replacement bushing will solve that problem, and not replacing the whole tensioner.
Radiator usually fails where the top hose meets the inlet.
Motor mounts collapsed? Could be. You haven't given a mileage on your car, but it might be due.
BTW, except for the daunting head gasket replacement, the above problems are DIY, and can be done for around $500 in parts (the $300 radiator being the most expensive). And many here have done the head gasket job.
Your head gasket can leak for years before actually being a real problem. When you start seeing oil in the coolant, or you can't keep the engine from overheating, that's the time to act.
2009 ML350 (84K) - Family vehicle
2001 CLK430 Cabriolet (71K) - Wife's car
2005 BMW 645CI (124K) - My daily driver
2012 Mustang V6 (60K) - Daughter's car