Varactor - D11 - an SVC251 can work there...
They are SMD now...
But if you can find one as a Diode package, just follow polarity.
The SMD also shows polarity but remember the BANDED end needs to go to the powered pad,
The unbanded end goes to the larger Ground Foil trace that D11 would use...
Don't know how a Varactor could get toasted in there unless it's been abused
You SHOULD TEST the pads for excessive voltage presence; power it up - check and test those pads to make sure they are at 5 volts MAX (the PLL's output voltage range to this pad is between 1 volt to as high a 4.5V DC)
Now if you are talking about D6 - the Clipper Diode for Driver and Final - any 1N4001~4003 would work just use one rated for 100PIV (to prevent problems) with a 3 A Surge rating. You should, while there is no part in there - check it for shorts - continuity across BANDED side (towards Driver/Final area) to Ground - any shorts need to be investigated, also check continuity from that same hole all the way to COLLECTOR of Driver and Final - make sure they show good. That needs to show contiinuity
When you have a melted diode like that - in the D6 spot, scorch marks et-all - that means the diode melted and also formed a short in the molten pellet until it epoxy case opened to pour out the smoke and metal to break the connection leaving a mess - acts like a fuse - and stinks!