gsub for numeric characters in string

Dear all,

I have what is a bit of a confusing question, so I hope that I can explain
clearly. Thank you for your help in advance.

I would like to do a replacement procedure on several strings, but the way
that I am currently going about it is not working.

I have defined "len", which is a series comprising the lengths of different
items, all preceded by a colon.

len

[1] ":328" ":154" ?":135"
[4] ":147" ":30" ?":50"
[7] ":252" ":45" ?";"

'lenplustate" is a series that is comprised of an attribute of each item
preceding the colon, followed by the length (as defined in len).

lenplusstate

[1] "1:328" ?"1:154" ? "4:135"
[4] "NA:147" "3:30" ? "2:50"
[7] "NA:252" "NA:45" ?"NA;"

"tree" is a string that gives the specific relationship (via parenthetical
notation) among the different items. Note that the lengths are included in
this tree (following the colon), and the name of each item (1-5) precedes a
colon. However, not every colon is preceded with a name (because there are
internal nodes in the tree structure).

tree

[1] "(*1*:328,((*5*:154,*2*:135):147,(*3*:30,*4*:50):252):45);"

I would like to replace the length with the lengthplusstate in the tree,
while removing the names, so that it looks like this:

theoreticalnewtree

[1] "(*1*:328,((*1*:154,*4*:135)NA:147,(*3*:30,*2*:50)NA:252)NA:45);"